[ClassLoader] Fix storing not-found classes in APC cache

This PR was merged into the 2.3 branch.

Discussion
----------

Fix performance (PHP5) and memory (PHP7) issues when using token_get_all

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #16868
| License       | MIT
| Doc PR        | -

Although it's not the case anymore on PHP 7, on PHP 5, `is_array` checks are much slower than `isset` checks.

Also from @peteward in #17384:
>  New PHP7 memory manager will not release small buckets to OS automatically in cases exposed by `token_get_all()`. This function call addition specifically for PHP7 will reclaim this memory to keep the footprint down of long processe

> See above ticket and suggested actions by PHP internals team for long-running tasks (https://bugs.php.net/70098) - I think `cache:clear/warmup` on a heavy app justifies this.

> We're running on cloud-based hosting platforms under memory limitations (Platform.sh). When memory is exceeded we're into swap and the cache clearing process goes from seconds to minutes for the initial deployment, which really slows our development workflow and also causes holding page delays.

Commits
-------

e555aad Add gc_mem_caches() call for PHP7 after itoken_get_all() as new memory manager will not release small buckets to OS automatically
d1f72d8 Fix perf and mem issue when using token_get_all

ApcClassLoader.php

@@ -16,8 +16,8 @@ namespace Symfony\Component\ClassLoader;
  *
  * It expects an object implementing a findFile method to find the file. This
  * allows using it as a wrapper around the other loaders of the component (the
- * ClassLoader for instance) but also around any other autoloaders following
- * this convention (the Composer one for instance).
+ * ClassLoader and the UniversalClassLoader for instance) but also around any
+ * other autoloaders following this convention (the Composer one for instance).
  *
  *     // with a Symfony autoloader
  *     use Symfony\Component\ClassLoader\ClassLoader;
@@ -67,8 +67,8 @@ class ApcClassLoader
      */
     public function __construct($prefix, $decorated)
     {
-        if (!extension_loaded('apc')) {
-            throw new \RuntimeException('Unable to use ApcClassLoader as APC is not enabled.');
+        if (!function_exists('apcu_fetch')) {
+            throw new \RuntimeException('Unable to use ApcClassLoader as APC is not installed.');
         }
 
         if (!method_exists($decorated, 'findFile')) {
@@ -122,8 +122,10 @@ class ApcClassLoader
      */
     public function findFile($class)
     {
-        if (false === $file = apc_fetch($this->prefix.$class)) {
-            apc_store($this->prefix.$class, $file = $this->decorated->findFile($class));
+        $file = apcu_fetch($this->prefix.$class, $success);
+
+        if (!$success) {
+            apcu_store($this->prefix.$class, $file = $this->decorated->findFile($class) ?: null);
         }
 
         return $file;

ApcUniversalClassLoader.php

@@ -0,0 +1,98 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\ClassLoader;
+
+/**
+ * ApcUniversalClassLoader implements a "universal" autoloader cached in APC for PHP 5.3.
+ *
+ * It is able to load classes that use either:
+ *
+ *  * The technical interoperability standards for PHP 5.3 namespaces and
+ *    class names (https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-0.md);
+ *
+ *  * The PEAR naming convention for classes (http://pear.php.net/).
+ *
+ * Classes from a sub-namespace or a sub-hierarchy of PEAR classes can be
+ * looked for in a list of locations to ease the vendoring of a sub-set of
+ * classes for large projects.
+ *
+ * Example usage:
+ *
+ *     require 'vendor/symfony/src/Symfony/Component/ClassLoader/UniversalClassLoader.php';
+ *     require 'vendor/symfony/src/Symfony/Component/ClassLoader/ApcUniversalClassLoader.php';
+ *
+ *     use Symfony\Component\ClassLoader\ApcUniversalClassLoader;
+ *
+ *     $loader = new ApcUniversalClassLoader('apc.prefix.');
+ *
+ *     // register classes with namespaces
+ *     $loader->registerNamespaces(array(
+ *         'Symfony\Component' => __DIR__.'/component',
+ *         'Symfony' => __DIR__.'/framework',
+ *         'Sensio' => array(__DIR__.'/src', __DIR__.'/vendor'),
+ *     ));
+ *
+ *     // register a library using the PEAR naming convention
+ *     $loader->registerPrefixes(array(
+ *         'Swift_' => __DIR__.'/Swift',
+ *     ));
+ *
+ *     // activate the autoloader
+ *     $loader->register();
+ *
+ * In this example, if you try to use a class in the Symfony\Component
+ * namespace or one of its children (Symfony\Component\Console for instance),
+ * the autoloader will first look for the class under the component/
+ * directory, and it will then fallback to the framework/ directory if not
+ * found before giving up.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ * @author Kris Wallsmith <kris@symfony.com>
+ */
+class ApcUniversalClassLoader extends UniversalClassLoader
+{
+    private $prefix;
+
+    /**
+     * Constructor.
+     *
+     * @param string $prefix A prefix to create a namespace in APC
+     *
+     * @throws \RuntimeException
+     */
+    public function __construct($prefix)
+    {
+        if (!function_exists('apcu_fetch')) {
+            throw new \RuntimeException('Unable to use ApcUniversalClassLoader as APC is not enabled.');
+        }
+
+        $this->prefix = $prefix;
+    }
+
+    /**
+     * Finds a file by class name while caching lookups to APC.
+     *
+     * @param string $class A class name to resolve to file
+     *
+     * @return string|null The path, if found
+     */
+    public function findFile($class)
+    {
+        $file = apcu_fetch($this->prefix.$class, $success);
+
+        if (!$success) {
+            apcu_store($this->prefix.$class, $file = parent::findFile($class) ?: null);
+        }
+
+        return $file;
+    }
+}

CHANGELOG.md

@@ -1,22 +1,6 @@
 CHANGELOG
 =========
 
-3.0.0
------
-
- * The DebugClassLoader class has been removed
- * The DebugUniversalClassLoader class has been removed
- * The UniversalClassLoader class has been removed
- * The ApcUniversalClassLoader class has been removed
-
-2.4.0
------
-
- * deprecated the UniversalClassLoader in favor of the ClassLoader class instead
- * deprecated the ApcUniversalClassLoader in favor of the ApcClassLoader class instead
- * deprecated the DebugUniversalClassLoader in favor of the DebugClassLoader class from the Debug component
- * deprecated the DebugClassLoader as it has been moved to the Debug component instead
-
 2.3.0
 -----
 

ClassCollectionLoader.php

@@ -43,14 +43,17 @@ class ClassCollectionLoader
 
         self::$loaded[$name] = true;
 
-        $declared = array_merge(get_declared_classes(), get_declared_interfaces(), get_declared_traits());
+        $declared = array_merge(get_declared_classes(), get_declared_interfaces());
+        if (function_exists('get_declared_traits')) {
+            $declared = array_merge($declared, get_declared_traits());
+        }
 
         if ($adaptive) {
             // don't include already declared classes
             $classes = array_diff($classes, $declared);
 
             // the cache is different depending on which classes are already declared
-            $name = $name.'-'.substr(hash('sha256', implode('|', $classes)), 0, 5);
+            $name = $name.'-'.substr(md5(implode('|', $classes)), 0, 5);
         }
 
         $classes = array_unique($classes);
@@ -113,8 +116,8 @@ class ClassCollectionLoader
         }
 
         // cache the core classes
-        if (!is_dir(dirname($cache))) {
-            mkdir(dirname($cache), 0777, true);
+        if (!is_dir($cacheDir) && !@mkdir($cacheDir, 0777, true) && !is_dir($cacheDir)) {
+            throw new \RuntimeException(sprintf('Class Collection Loader was not able to create directory "%s"', $cacheDir));
         }
         self::writeCacheFile($cache, '<?php '.$content);
 
@@ -146,8 +149,9 @@ class ClassCollectionLoader
         $inNamespace = false;
         $tokens = token_get_all($source);
 
-        for (reset($tokens); false !== $token = current($tokens); next($tokens)) {
-            if (is_string($token)) {
+        for ($i = 0; isset($tokens[$i]); ++$i) {
+            $token = $tokens[$i];
+            if (!isset($token[1]) || 'b"' === $token) {
                 $rawChunk .= $token;
             } elseif (in_array($token[0], array(T_COMMENT, T_DOC_COMMENT))) {
                 // strip comments
@@ -159,12 +163,12 @@ class ClassCollectionLoader
                 $rawChunk .= $token[1];
 
                 // namespace name and whitespaces
-                while (($t = next($tokens)) && is_array($t) && in_array($t[0], array(T_WHITESPACE, T_NS_SEPARATOR, T_STRING))) {
-                    $rawChunk .= $t[1];
+                while (isset($tokens[++$i][1]) && in_array($tokens[$i][0], array(T_WHITESPACE, T_NS_SEPARATOR, T_STRING))) {
+                    $rawChunk .= $tokens[$i][1];
                 }
-                if ('{' === $t) {
+                if ('{' === $tokens[$i]) {
                     $inNamespace = false;
-                    prev($tokens);
+                    --$i;
                 } else {
                     $rawChunk = rtrim($rawChunk)."\n{";
                     $inNamespace = true;
@@ -172,8 +176,8 @@ class ClassCollectionLoader
             } elseif (T_START_HEREDOC === $token[0]) {
                 $output .= self::compressCode($rawChunk).$token[1];
                 do {
-                    $token = next($tokens);
-                    $output .= is_string($token) ? $token : $token[1];
+                    $token = $tokens[++$i];
+                    $output .= isset($token[1]) && 'b"' !== $token ? $token[1] : $token;
                 } while ($token[0] !== T_END_HEREDOC);
                 $output .= "\n";
                 $rawChunk = '';
@@ -189,7 +193,15 @@ class ClassCollectionLoader
             $rawChunk .= "}\n";
         }
 
-        return $output.self::compressCode($rawChunk);
+        $output .= self::compressCode($rawChunk);
+
+        if (PHP_VERSION_ID >= 70000) {
+            // PHP 7 memory manager will not release after token_get_all(), see https://bugs.php.net/70098
+            unset($tokens, $rawChunk);
+            gc_mem_caches();
+        }
+
+        return $output;
     }
 
     /**
@@ -280,10 +292,12 @@ class ClassCollectionLoader
 
         $traits = array();
 
-        foreach ($classes as $c) {
-            foreach (self::resolveDependencies(self::computeTraitDeps($c), $c) as $trait) {
-                if ($trait !== $c) {
-                    $traits[] = $trait;
+        if (method_exists('ReflectionClass', 'getTraits')) {
+            foreach ($classes as $c) {
+                foreach (self::resolveDependencies(self::computeTraitDeps($c), $c) as $trait) {
+                    if ($trait !== $c) {
+                        $traits[] = $trait;
+                    }
                 }
             }
         }

ClassLoader.php

@@ -97,7 +97,7 @@ class ClassLoader
                     $paths
                 ));
             } elseif (!in_array($paths, $this->prefixes[$prefix])) {
-                 $this->prefixes[$prefix][] = $paths;
+                $this->prefixes[$prefix][] = $paths;
             }
         } else {
             $this->prefixes[$prefix] = array_unique((array) $paths);

ClassMapGenerator.php

@@ -11,6 +11,14 @@
 
 namespace Symfony\Component\ClassLoader;
 
+if (!defined('SYMFONY_TRAIT')) {
+    if (PHP_VERSION_ID >= 50400) {
+        define('SYMFONY_TRAIT', T_TRAIT);
+    } else {
+        define('SYMFONY_TRAIT', 0);
+    }
+}
+
 /**
  * ClassMapGenerator.
  *
@@ -64,6 +72,11 @@ class ClassMapGenerator
 
             $classes = self::findClasses($path);
 
+            if (PHP_VERSION_ID >= 70000) {
+                // PHP 7 memory manager will not release after token_get_all(), see https://bugs.php.net/70098
+                gc_mem_caches();
+            }
+
             foreach ($classes as $class) {
                 $map[$class] = $path;
             }
@@ -87,10 +100,10 @@ class ClassMapGenerator
         $classes = array();
 
         $namespace = '';
-        for ($i = 0, $max = count($tokens); $i < $max; ++$i) {
+        for ($i = 0; isset($tokens[$i]); ++$i) {
             $token = $tokens[$i];
 
-            if (is_string($token)) {
+            if (!isset($token[1])) {
                 continue;
             }
 
@@ -100,20 +113,20 @@ class ClassMapGenerator
                 case T_NAMESPACE:
                     $namespace = '';
                     // If there is a namespace, extract it
-                    while (($t = $tokens[++$i]) && is_array($t)) {
-                        if (in_array($t[0], array(T_STRING, T_NS_SEPARATOR))) {
-                            $namespace .= $t[1];
+                    while (isset($tokens[++$i][1])) {
+                        if (in_array($tokens[$i][0], array(T_STRING, T_NS_SEPARATOR))) {
+                            $namespace .= $tokens[$i][1];
                         }
                     }
                     $namespace .= '\\';
                     break;
                 case T_CLASS:
                 case T_INTERFACE:
-                case T_TRAIT:
+                case SYMFONY_TRAIT:
                     // Skip usage of ::class constant
                     $isClassConstant = false;
                     for ($j = $i - 1; $j > 0; --$j) {
-                        if (is_string($tokens[$j])) {
+                        if (!isset($tokens[$j][1])) {
                             break;
                         }
 
@@ -126,14 +139,15 @@ class ClassMapGenerator
                     }
 
                     if ($isClassConstant) {
-                        continue;
+                        break;
                     }
 
                     // Find the classname
-                    while (($t = $tokens[++$i]) && is_array($t)) {
+                    while (isset($tokens[++$i][1])) {
+                        $t = $tokens[$i];
                         if (T_STRING === $t[0]) {
                             $class .= $t[1];
-                        } elseif ($class !== '' && T_WHITESPACE == $t[0]) {
+                        } elseif ('' !== $class && T_WHITESPACE === $t[0]) {
                             break;
                         }
                     }

DebugClassLoader.php

@@ -0,0 +1,105 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\ClassLoader;
+
+/**
+ * Autoloader checking if the class is really defined in the file found.
+ *
+ * The DebugClassLoader will wrap all registered autoloaders providing a
+ * findFile method and will throw an exception if a file is found but does
+ * not declare the class.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ * @author Christophe Coevoet <stof@notk.org>
+ */
+class DebugClassLoader
+{
+    private $classFinder;
+
+    /**
+     * Constructor.
+     *
+     * @param object $classFinder
+     */
+    public function __construct($classFinder)
+    {
+        $this->classFinder = $classFinder;
+    }
+
+    /**
+     * Replaces all autoloaders implementing a findFile method by a DebugClassLoader wrapper.
+     */
+    public static function enable()
+    {
+        if (!is_array($functions = spl_autoload_functions())) {
+            return;
+        }
+
+        foreach ($functions as $function) {
+            spl_autoload_unregister($function);
+        }
+
+        foreach ($functions as $function) {
+            if (is_array($function) && !$function[0] instanceof self && method_exists($function[0], 'findFile')) {
+                $function = array(new static($function[0]), 'loadClass');
+            }
+
+            spl_autoload_register($function);
+        }
+    }
+
+    /**
+     * Unregisters this instance as an autoloader.
+     */
+    public function unregister()
+    {
+        spl_autoload_unregister(array($this, 'loadClass'));
+    }
+
+    /**
+     * Finds a file by class name.
+     *
+     * @param string $class A class name to resolve to file
+     *
+     * @return string|null
+     */
+    public function findFile($class)
+    {
+        return $this->classFinder->findFile($class) ?: null;
+    }
+
+    /**
+     * Loads the given class or interface.
+     *
+     * @param string $class The name of the class
+     *
+     * @return bool|null True, if loaded
+     *
+     * @throws \RuntimeException
+     */
+    public function loadClass($class)
+    {
+        if ($file = $this->classFinder->findFile($class)) {
+            require $file;
+
+            if (!class_exists($class, false) && !interface_exists($class, false) && (!function_exists('trait_exists') || !trait_exists($class, false))) {
+                if (false !== strpos($class, '/')) {
+                    throw new \RuntimeException(sprintf('Trying to autoload a class with an invalid name "%s". Be careful that the namespace separator is "\" in PHP, not "/".', $class));
+                }
+
+                throw new \RuntimeException(sprintf('The autoloader expected class "%s" to be defined in file "%s". The file was found but the class was not in it, the class name or namespace probably has a typo.', $class, $file));
+            }
+
+            return true;
+        }
+    }
+}

DebugUniversalClassLoader.php

@@ -0,0 +1,63 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\ClassLoader;
+
+/**
+ * Checks that the class is actually declared in the included file.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class DebugUniversalClassLoader extends UniversalClassLoader
+{
+    /**
+     * Replaces all regular UniversalClassLoader instances by a DebugUniversalClassLoader ones.
+     */
+    public static function enable()
+    {
+        if (!is_array($functions = spl_autoload_functions())) {
+            return;
+        }
+
+        foreach ($functions as $function) {
+            spl_autoload_unregister($function);
+        }
+
+        foreach ($functions as $function) {
+            if (is_array($function) && $function[0] instanceof UniversalClassLoader) {
+                $loader = new static();
+                $loader->registerNamespaceFallbacks($function[0]->getNamespaceFallbacks());
+                $loader->registerPrefixFallbacks($function[0]->getPrefixFallbacks());
+                $loader->registerNamespaces($function[0]->getNamespaces());
+                $loader->registerPrefixes($function[0]->getPrefixes());
+                $loader->useIncludePath($function[0]->getUseIncludePath());
+
+                $function[0] = $loader;
+            }
+
+            spl_autoload_register($function);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function loadClass($class)
+    {
+        if ($file = $this->findFile($class)) {
+            require $file;
+
+            if (!class_exists($class, false) && !interface_exists($class, false) && (!function_exists('trait_exists') || !trait_exists($class, false))) {
+                throw new \RuntimeException(sprintf('The autoloader expected class "%s" to be defined in file "%s". The file was found but the class was not in it, the class name or namespace probably has a typo.', $class, $file));
+            }
+        }
+    }
+}

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2004-2015 Fabien Potencier
+Copyright (c) 2004-2016 Fabien Potencier
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

Psr4ClassLoader.php

@@ -1,93 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ClassLoader;
-
-/**
- * A PSR-4 compatible class loader.
- *
- * See http://www.php-fig.org/psr/psr-4/
- *
- * @author Alexander M. Turek <me@derrabus.de>
- */
-class Psr4ClassLoader
-{
-    /**
-     * @var array
-     */
-    private $prefixes = array();
-
-    /**
-     * @param string $prefix
-     * @param string $baseDir
-     */
-    public function addPrefix($prefix, $baseDir)
-    {
-        $prefix = trim($prefix, '\\').'\\';
-        $baseDir = rtrim($baseDir, DIRECTORY_SEPARATOR).DIRECTORY_SEPARATOR;
-        $this->prefixes[] = array($prefix, $baseDir);
-    }
-
-    /**
-     * @param string $class
-     *
-     * @return string|null
-     */
-    public function findFile($class)
-    {
-        $class = ltrim($class, '\\');
-
-        foreach ($this->prefixes as list($currentPrefix, $currentBaseDir)) {
-            if (0 === strpos($class, $currentPrefix)) {
-                $classWithoutPrefix = substr($class, strlen($currentPrefix));
-                $file = $currentBaseDir.str_replace('\\', DIRECTORY_SEPARATOR, $classWithoutPrefix).'.php';
-                if (file_exists($file)) {
-                    return $file;
-                }
-            }
-        }
-    }
-
-    /**
-     * @param string $class
-     *
-     * @return bool
-     */
-    public function loadClass($class)
-    {
-        $file = $this->findFile($class);
-        if (null !== $file) {
-            require $file;
-
-            return true;
-        }
-
-        return false;
-    }
-
-    /**
-     * Registers this instance as an autoloader.
-     *
-     * @param bool $prepend
-     */
-    public function register($prepend = false)
-    {
-        spl_autoload_register(array($this, 'loadClass'), true, $prepend);
-    }
-
-    /**
-     * Removes this instance from the registered autoloaders.
-     */
-    public function unregister()
-    {
-        spl_autoload_unregister(array($this, 'loadClass'));
-    }
-}

README.md

@@ -1,85 +1,14 @@
 ClassLoader Component
 =====================
 
-ClassLoader loads your project classes automatically if they follow some
-standard PHP conventions.
-
-The ClassLoader object is able to autoload classes that implement the PSR-0
-standard or the PEAR naming convention.
-
-First, register the autoloader:
-
-```php
-require_once __DIR__.'/src/Symfony/Component/ClassLoader/ClassLoader.php';
-
-use Symfony\Component\ClassLoader\ClassLoader;
-
-$loader = new ClassLoader();
-$loader->register();
-```
-
-Then, register some namespaces with the `addPrefix()` method:
-
-```php
-$loader->addPrefix('Symfony', __DIR__.'/src');
-$loader->addPrefix('Monolog', __DIR__.'/vendor/monolog/src');
-```
-
-The `addPrefix()` method takes a namespace prefix and a path where to look for
-the classes as arguments.
-
-You can also register a sub-namespaces:
-
-```php
-$loader->addPrefix('Doctrine\\Common', __DIR__.'/vendor/doctrine-common/lib');
-```
-
-The order of registration is significant and the first registered namespace
-takes precedence over later registered one.
-
-You can also register more than one path for a given namespace:
-
-```php
-$loader->addPrefix('Symfony', array(__DIR__.'/src', __DIR__.'/symfony/src'));
-```
-
-Alternatively, you can use the `addPrefixes()` method to register more
-than one namespace at once:
-
-```php
-$loader->addPrefixes(array(
-    'Symfony' => array(__DIR__.'/src', __DIR__.'/symfony/src'),
-    'Doctrine\\Common' => __DIR__.'/vendor/doctrine-common/lib',
-    'Doctrine' => __DIR__.'/vendor/doctrine/lib',
-    'Monolog' => __DIR__.'/vendor/monolog/src',
-));
-```
-
-For better performance, you can use the APC class loader:
-
-```php
-require_once __DIR__.'/src/Symfony/Component/ClassLoader/ClassLoader.php';
-require_once __DIR__.'/src/Symfony/Component/ClassLoader/ApcClassLoader.php';
-
-use Symfony\Component\ClassLoader\ClassLoader;
-use Symfony\Component\ClassLoader\ApcClassLoader;
-
-$loader = new ClassLoader();
-$loader->addPrefix('Symfony', __DIR__.'/src');
-
-$loader = new ApcClassLoader('apc.prefix.', $loader);
-$loader->register();
-```
-
-Furthermore, the component provides tools to aggregate classes into a single
-file, which is especially useful to improve performance on servers that do not
-provide byte caches.
+The ClassLoader component provides tools to autoload your classes and cache
+their locations for performance.
 
 Resources
 ---------
 
-You can run the unit tests with the following command:
-
-    $ cd path/to/Symfony/Component/ClassLoader/
-    $ composer install
-    $ phpunit
+  * [Documentation](https://symfony.com/doc/current/components/class_loader/index.html)
+  * [Contributing](https://symfony.com/doc/current/contributing/index.html)
+  * [Report issues](https://github.com/symfony/symfony/issues) and
+    [send Pull Requests](https://github.com/symfony/symfony/pulls)
+    in the [main Symfony repository](https://github.com/symfony/symfony)

Tests/ApcUniversalClassLoaderTest.php

@@ -11,18 +11,14 @@
 
 namespace Symfony\Component\ClassLoader\Tests;
 
-use Symfony\Component\ClassLoader\ApcClassLoader;
-use Symfony\Component\ClassLoader\ClassLoader;
+use Symfony\Component\ClassLoader\ApcUniversalClassLoader;
 
-/**
- * @requires extension apc
- */
-class ApcClassLoaderTest extends \PHPUnit_Framework_TestCase
+class ApcUniversalClassLoaderTest extends \PHPUnit_Framework_TestCase
 {
     protected function setUp()
     {
         if (ini_get('apc.enabled') && ini_get('apc.enable_cli')) {
-            apc_clear_cache('user');
+            apcu_clear_cache();
         } else {
             $this->markTestSkipped('APC is not enabled.');
         }
@@ -31,57 +27,51 @@ class ApcClassLoaderTest extends \PHPUnit_Framework_TestCase
     protected function tearDown()
     {
         if (ini_get('apc.enabled') && ini_get('apc.enable_cli')) {
-            apc_clear_cache('user');
+            apcu_clear_cache();
         }
     }
 
     public function testConstructor()
     {
-        $loader = new ClassLoader();
-        $loader->addPrefix('Apc\Namespaced', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $loader = new ApcUniversalClassLoader('test.prefix.');
+        $loader->registerNamespace('Apc\Namespaced', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
 
-        $loader = new ApcClassLoader('test.prefix.', $loader);
-
-        $this->assertEquals($loader->findFile('\Apc\Namespaced\FooBar'), apc_fetch('test.prefix.\Apc\Namespaced\FooBar'), '__construct() takes a prefix as its first argument');
+        $this->assertEquals($loader->findFile('\Apc\Namespaced\FooBar'), apcu_fetch('test.prefix.\Apc\Namespaced\FooBar'), '__construct() takes a prefix as its first argument');
     }
 
-    /**
-     * @dataProvider getLoadClassTests
-     */
-    public function testLoadClass($className, $testClassName, $message)
-    {
-        $loader = new ClassLoader();
-        $loader->addPrefix('Apc\Namespaced', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
-        $loader->addPrefix('Apc_Pearlike_', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
-
-        $loader = new ApcClassLoader('test.prefix.', $loader);
-        $loader->loadClass($testClassName);
-        $this->assertTrue(class_exists($className), $message);
-    }
+   /**
+    * @dataProvider getLoadClassTests
+    */
+   public function testLoadClass($className, $testClassName, $message)
+   {
+       $loader = new ApcUniversalClassLoader('test.prefix.');
+       $loader->registerNamespace('Apc\Namespaced', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+       $loader->registerPrefix('Apc_Pearlike_', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+       $loader->loadClass($testClassName);
+       $this->assertTrue(class_exists($className), $message);
+   }
 
     public function getLoadClassTests()
     {
         return array(
            array('\\Apc\\Namespaced\\Foo', 'Apc\\Namespaced\\Foo',   '->loadClass() loads Apc\Namespaced\Foo class'),
            array('Apc_Pearlike_Foo',    'Apc_Pearlike_Foo',      '->loadClass() loads Apc_Pearlike_Foo class'),
-        );
+       );
     }
 
-    /**
-     * @dataProvider getLoadClassFromFallbackTests
-     */
-    public function testLoadClassFromFallback($className, $testClassName, $message)
-    {
-        $loader = new ClassLoader();
-        $loader->addPrefix('Apc\Namespaced', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
-        $loader->addPrefix('Apc_Pearlike_', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
-        $loader->addPrefix('', array(__DIR__.DIRECTORY_SEPARATOR.'Fixtures/Apc/fallback'));
-
-        $loader = new ApcClassLoader('test.prefix.fallback', $loader);
-        $loader->loadClass($testClassName);
-
-        $this->assertTrue(class_exists($className), $message);
-    }
+   /**
+    * @dataProvider getLoadClassFromFallbackTests
+    */
+   public function testLoadClassFromFallback($className, $testClassName, $message)
+   {
+       $loader = new ApcUniversalClassLoader('test.prefix.fallback');
+       $loader->registerNamespace('Apc\Namespaced', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+       $loader->registerPrefix('Apc_Pearlike_', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+       $loader->registerNamespaceFallbacks(array(__DIR__.DIRECTORY_SEPARATOR.'Fixtures/Apc/fallback'));
+       $loader->registerPrefixFallbacks(array(__DIR__.DIRECTORY_SEPARATOR.'Fixtures/Apc/fallback'));
+       $loader->loadClass($testClassName);
+       $this->assertTrue(class_exists($className), $message);
+   }
 
     public function getLoadClassFromFallbackTests()
     {
@@ -93,19 +83,18 @@ class ApcClassLoaderTest extends \PHPUnit_Framework_TestCase
        );
     }
 
-    /**
-     * @dataProvider getLoadClassNamespaceCollisionTests
-     */
-    public function testLoadClassNamespaceCollision($namespaces, $className, $message)
-    {
-        $loader = new ClassLoader();
-        $loader->addPrefixes($namespaces);
+   /**
+    * @dataProvider getLoadClassNamespaceCollisionTests
+    */
+   public function testLoadClassNamespaceCollision($namespaces, $className, $message)
+   {
+       $loader = new ApcUniversalClassLoader('test.prefix.collision.');
+       $loader->registerNamespaces($namespaces);
 
-        $loader = new ApcClassLoader('test.prefix.collision.', $loader);
-        $loader->loadClass($className);
+       $loader->loadClass($className);
 
-        $this->assertTrue(class_exists($className), $message);
-    }
+       $this->assertTrue(class_exists($className), $message);
+   }
 
     public function getLoadClassNamespaceCollisionTests()
     {
@@ -142,22 +131,20 @@ class ApcClassLoaderTest extends \PHPUnit_Framework_TestCase
                'Apc\NamespaceCollision\A\B\Bar',
                '->loadClass() loads NamespaceCollision\A\B\Bar from beta.',
            ),
-        );
+       );
     }
 
-    /**
-     * @dataProvider getLoadClassPrefixCollisionTests
-     */
-    public function testLoadClassPrefixCollision($prefixes, $className, $message)
-    {
-        $loader = new ClassLoader();
-        $loader->addPrefixes($prefixes);
+   /**
+    * @dataProvider getLoadClassPrefixCollisionTests
+    */
+   public function testLoadClassPrefixCollision($prefixes, $className, $message)
+   {
+       $loader = new ApcUniversalClassLoader('test.prefix.collision.');
+       $loader->registerPrefixes($prefixes);
 
-        $loader = new ApcClassLoader('test.prefix.collision.', $loader);
-        $loader->loadClass($className);
-
-        $this->assertTrue(class_exists($className), $message);
-    }
+       $loader->loadClass($className);
+       $this->assertTrue(class_exists($className), $message);
+   }
 
     public function getLoadClassPrefixCollisionTests()
     {
@@ -194,6 +181,6 @@ class ApcClassLoaderTest extends \PHPUnit_Framework_TestCase
                'ApcPrefixCollision_A_B_Bar',
                '->loadClass() loads ApcPrefixCollision_A_B_Bar from beta.',
            ),
-        );
+       );
     }
 }

Tests/ClassCollectionLoaderTest.php

@@ -20,6 +20,9 @@ require_once __DIR__.'/Fixtures/ClassesWithParents/A.php';
 
 class ClassCollectionLoaderTest extends \PHPUnit_Framework_TestCase
 {
+    /**
+     * @requires PHP 5.4
+     */
     public function testTraitDependencies()
     {
         require_once __DIR__.'/Fixtures/deps/traits.php';
@@ -91,6 +94,7 @@ class ClassCollectionLoaderTest extends \PHPUnit_Framework_TestCase
 
     /**
      * @dataProvider getDifferentOrdersForTraits
+     * @requires PHP 5.4
      */
     public function testClassWithTraitsReordering(array $classes)
     {
@@ -134,6 +138,9 @@ class ClassCollectionLoaderTest extends \PHPUnit_Framework_TestCase
         );
     }
 
+    /**
+     * @requires PHP 5.4
+     */
     public function testFixClassWithTraitsOrdering()
     {
         require_once __DIR__.'/Fixtures/ClassesWithParents/CTrait.php';
@@ -234,26 +241,26 @@ class ClassCollectionLoaderTest extends \PHPUnit_Framework_TestCase
 
         spl_autoload_unregister($r);
 
-        $this->assertEquals(<<<EOF
+        $this->assertEquals(<<<'EOF'
 namespace Namespaced
 {
 class WithComments
 {
-public static \$loaded = true;
+public static $loaded = true;
 }
-\$string ='string should not be   modified {\$string}';
-\$heredoc = (<<<HD
+$string ='string should not be   modified {$string}';
+$heredoc = (<<<HD
 
 
-Heredoc should not be   modified {\$string}
+Heredoc should not be   modified {$string}
 
 
 HD
 );
-\$nowdoc =<<<'ND'
+$nowdoc =<<<'ND'
 
 
-Nowdoc should not be   modified {\$string}
+Nowdoc should not be   modified {$string}
 
 
 ND
@@ -263,7 +270,7 @@ namespace
 {
 class Pearlike_WithComments
 {
-public static \$loaded = true;
+public static $loaded = true;
 }
 }
 EOF

Tests/ClassLoaderTest.php

@@ -72,7 +72,7 @@ class ClassLoaderTest extends \PHPUnit_Framework_TestCase
     public function getLoadNonexistentClassTests()
     {
         return array(
-            array('\\Pearlike3_Bar', '\\Pearlike3_Bar', '->loadClass() loads non existing Pearlike3_Bar class with a leading slash'),
+            array('\\Pearlike3_Bar', '\\Pearlike3_Bar', '->loadClass() loads non exising Pearlike3_Bar class with a leading slash'),
         );
     }
 

Tests/ClassMapGeneratorTest.php

@@ -22,7 +22,7 @@ class ClassMapGeneratorTest extends \PHPUnit_Framework_TestCase
 
     public function prepare_workspace()
     {
-        $this->workspace = rtrim(sys_get_temp_dir(), DIRECTORY_SEPARATOR).DIRECTORY_SEPARATOR.time().mt_rand(0, 1000);
+        $this->workspace = sys_get_temp_dir().'/'.microtime(true).'.'.mt_rand();
         mkdir($this->workspace, 0777, true);
         $this->workspace = realpath($this->workspace);
     }
@@ -102,18 +102,24 @@ class ClassMapGeneratorTest extends \PHPUnit_Framework_TestCase
                 'ClassMap\\SomeParent' => realpath(__DIR__).'/Fixtures/classmap/SomeParent.php',
                 'ClassMap\\SomeClass' => realpath(__DIR__).'/Fixtures/classmap/SomeClass.php',
             )),
-            array(__DIR__.'/Fixtures/php5.4', array(
+        );
+
+        if (PHP_VERSION_ID >= 50400) {
+            $data[] = array(__DIR__.'/Fixtures/php5.4', array(
                 'TFoo' => __DIR__.'/Fixtures/php5.4/traits.php',
                 'CFoo' => __DIR__.'/Fixtures/php5.4/traits.php',
                 'Foo\\TBar' => __DIR__.'/Fixtures/php5.4/traits.php',
                 'Foo\\IBar' => __DIR__.'/Fixtures/php5.4/traits.php',
                 'Foo\\TFooBar' => __DIR__.'/Fixtures/php5.4/traits.php',
                 'Foo\\CBar' => __DIR__.'/Fixtures/php5.4/traits.php',
-            )),
-            array(__DIR__.'/Fixtures/php5.5', array(
+            ));
+        }
+
+        if (PHP_VERSION_ID >= 50500) {
+            $data[] = array(__DIR__.'/Fixtures/php5.5', array(
                 'ClassCons\\Foo' => __DIR__.'/Fixtures/php5.5/class_cons.php',
-            )),
-        );
+            ));
+        }
 
         return $data;
     }

Tests/DebugClassLoaderTest.php

@@ -0,0 +1,52 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\ClassLoader\Tests;
+
+use Symfony\Component\ClassLoader\ClassLoader;
+use Symfony\Component\ClassLoader\DebugClassLoader;
+
+class DebugClassLoaderTest extends \PHPUnit_Framework_TestCase
+{
+    private $loader;
+
+    protected function setUp()
+    {
+        $this->loader = new ClassLoader();
+        spl_autoload_register(array($this->loader, 'loadClass'));
+    }
+
+    protected function tearDown()
+    {
+        spl_autoload_unregister(array($this->loader, 'loadClass'));
+    }
+
+    public function testIdempotence()
+    {
+        DebugClassLoader::enable();
+        DebugClassLoader::enable();
+
+        $functions = spl_autoload_functions();
+        foreach ($functions as $function) {
+            if (is_array($function) && $function[0] instanceof DebugClassLoader) {
+                $reflClass = new \ReflectionClass($function[0]);
+                $reflProp = $reflClass->getProperty('classFinder');
+                $reflProp->setAccessible(true);
+
+                $this->assertNotInstanceOf('Symfony\Component\ClassLoader\DebugClassLoader', $reflProp->getValue($function[0]));
+
+                return;
+            }
+        }
+
+        throw new \Exception('DebugClassLoader did not register');
+    }
+}

Tests/Fixtures/psr-4/Class_With_Underscores.php

@@ -1,7 +0,0 @@
-<?php
-
-namespace Acme\DemoLib;
-
-class Class_With_Underscores
-{
-}

Tests/Fixtures/psr-4/Foo.php

@@ -1,7 +0,0 @@
-<?php
-
-namespace Acme\DemoLib;
-
-class Foo
-{
-}

Tests/Fixtures/psr-4/Lets/Go/Deeper/Class_With_Underscores.php

@@ -1,7 +0,0 @@
-<?php
-
-namespace Acme\DemoLib\Lets\Go\Deeper;
-
-class Class_With_Underscores
-{
-}

Tests/Fixtures/psr-4/Lets/Go/Deeper/Foo.php

@@ -1,7 +0,0 @@
-<?php
-
-namespace Acme\DemoLib\Lets\Go\Deeper;
-
-class Foo
-{
-}

Tests/Psr4ClassLoaderTest.php

@@ -1,71 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\ClassLoader\Tests;
-
-use Symfony\Component\ClassLoader\Psr4ClassLoader;
-
-class Psr4ClassLoaderTest extends \PHPUnit_Framework_TestCase
-{
-    /**
-     * @param string $className
-     * @dataProvider getLoadClassTests
-     */
-    public function testLoadClass($className)
-    {
-        $loader = new Psr4ClassLoader();
-        $loader->addPrefix(
-            'Acme\\DemoLib',
-            __DIR__.DIRECTORY_SEPARATOR.'Fixtures'.DIRECTORY_SEPARATOR.'psr-4'
-        );
-        $loader->loadClass($className);
-        $this->assertTrue(class_exists($className), sprintf('loadClass() should load %s', $className));
-    }
-
-    /**
-     * @return array
-     */
-    public function getLoadClassTests()
-    {
-        return array(
-            array('Acme\\DemoLib\\Foo'),
-            array('Acme\\DemoLib\\Class_With_Underscores'),
-            array('Acme\\DemoLib\\Lets\\Go\\Deeper\\Foo'),
-            array('Acme\\DemoLib\\Lets\\Go\\Deeper\\Class_With_Underscores'),
-        );
-    }
-
-    /**
-     * @param string $className
-     * @dataProvider getLoadNonexistentClassTests
-     */
-    public function testLoadNonexistentClass($className)
-    {
-        $loader = new Psr4ClassLoader();
-        $loader->addPrefix(
-            'Acme\\DemoLib',
-            __DIR__.DIRECTORY_SEPARATOR.'Fixtures'.DIRECTORY_SEPARATOR.'psr-4'
-        );
-        $loader->loadClass($className);
-        $this->assertFalse(class_exists($className), sprintf('loadClass() should not load %s', $className));
-    }
-
-    /**
-     * @return array
-     */
-    public function getLoadNonexistentClassTests()
-    {
-        return array(
-            array('Acme\\DemoLib\\I_Do_Not_Exist'),
-            array('UnknownVendor\\SomeLib\\I_Do_Not_Exist'),
-        );
-    }
-}

Tests/UniversalClassLoaderTest.php

@@ -0,0 +1,220 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\ClassLoader\Tests;
+
+use Symfony\Component\ClassLoader\UniversalClassLoader;
+
+class UniversalClassLoaderTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @dataProvider getLoadClassTests
+     */
+    public function testLoadClass($className, $testClassName, $message)
+    {
+        $loader = new UniversalClassLoader();
+        $loader->registerNamespace('Namespaced', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $loader->registerPrefix('Pearlike_', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $this->assertTrue($loader->loadClass($testClassName));
+        $this->assertTrue(class_exists($className), $message);
+    }
+
+    public function getLoadClassTests()
+    {
+        return array(
+            array('\\Namespaced\\Foo', 'Namespaced\\Foo',   '->loadClass() loads Namespaced\Foo class'),
+            array('\\Pearlike_Foo',    'Pearlike_Foo',      '->loadClass() loads Pearlike_Foo class'),
+        );
+    }
+
+    public function testUseIncludePath()
+    {
+        $loader = new UniversalClassLoader();
+        $this->assertFalse($loader->getUseIncludePath());
+
+        $this->assertNull($loader->findFile('Foo'));
+
+        $includePath = get_include_path();
+
+        $loader->useIncludePath(true);
+        $this->assertTrue($loader->getUseIncludePath());
+
+        set_include_path(__DIR__.'/Fixtures/includepath'.PATH_SEPARATOR.$includePath);
+
+        $this->assertEquals(__DIR__.DIRECTORY_SEPARATOR.'Fixtures'.DIRECTORY_SEPARATOR.'includepath'.DIRECTORY_SEPARATOR.'Foo.php', $loader->findFile('Foo'));
+
+        set_include_path($includePath);
+    }
+
+    public function testGetNamespaces()
+    {
+        $loader = new UniversalClassLoader();
+        $loader->registerNamespace('Foo', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $loader->registerNamespace('Bar', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $loader->registerNamespace('Bas', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $namespaces = $loader->getNamespaces();
+        $this->assertArrayHasKey('Foo', $namespaces);
+        $this->assertArrayNotHasKey('Foo1', $namespaces);
+        $this->assertArrayHasKey('Bar', $namespaces);
+        $this->assertArrayHasKey('Bas', $namespaces);
+    }
+
+    public function testGetPrefixes()
+    {
+        $loader = new UniversalClassLoader();
+        $loader->registerPrefix('Foo', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $loader->registerPrefix('Bar', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $loader->registerPrefix('Bas', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $prefixes = $loader->getPrefixes();
+        $this->assertArrayHasKey('Foo', $prefixes);
+        $this->assertArrayNotHasKey('Foo1', $prefixes);
+        $this->assertArrayHasKey('Bar', $prefixes);
+        $this->assertArrayHasKey('Bas', $prefixes);
+    }
+
+    /**
+     * @dataProvider getLoadClassFromFallbackTests
+     */
+    public function testLoadClassFromFallback($className, $testClassName, $message)
+    {
+        $loader = new UniversalClassLoader();
+        $loader->registerNamespace('Namespaced', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $loader->registerPrefix('Pearlike_', __DIR__.DIRECTORY_SEPARATOR.'Fixtures');
+        $loader->registerNamespaceFallbacks(array(__DIR__.DIRECTORY_SEPARATOR.'Fixtures/fallback'));
+        $loader->registerPrefixFallbacks(array(__DIR__.DIRECTORY_SEPARATOR.'Fixtures/fallback'));
+        $this->assertTrue($loader->loadClass($testClassName));
+        $this->assertTrue(class_exists($className), $message);
+    }
+
+    public function getLoadClassFromFallbackTests()
+    {
+        return array(
+            array('\\Namespaced\\Baz',    'Namespaced\\Baz',    '->loadClass() loads Namespaced\Baz class'),
+            array('\\Pearlike_Baz',       'Pearlike_Baz',       '->loadClass() loads Pearlike_Baz class'),
+            array('\\Namespaced\\FooBar', 'Namespaced\\FooBar', '->loadClass() loads Namespaced\Baz class from fallback dir'),
+            array('\\Pearlike_FooBar',    'Pearlike_FooBar',    '->loadClass() loads Pearlike_Baz class from fallback dir'),
+        );
+    }
+
+    public function testRegisterPrefixFallback()
+    {
+        $loader = new UniversalClassLoader();
+        $loader->registerPrefixFallback(__DIR__.DIRECTORY_SEPARATOR.'Fixtures/fallback');
+        $this->assertEquals(array(__DIR__.DIRECTORY_SEPARATOR.'Fixtures/fallback'), $loader->getPrefixFallbacks());
+    }
+
+    public function testRegisterNamespaceFallback()
+    {
+        $loader = new UniversalClassLoader();
+        $loader->registerNamespaceFallback(__DIR__.DIRECTORY_SEPARATOR.'Fixtures/Namespaced/fallback');
+        $this->assertEquals(array(__DIR__.DIRECTORY_SEPARATOR.'Fixtures/Namespaced/fallback'), $loader->getNamespaceFallbacks());
+    }
+
+    /**
+     * @dataProvider getLoadClassNamespaceCollisionTests
+     */
+    public function testLoadClassNamespaceCollision($namespaces, $className, $message)
+    {
+        $loader = new UniversalClassLoader();
+        $loader->registerNamespaces($namespaces);
+
+        $this->assertTrue($loader->loadClass($className));
+        $this->assertTrue(class_exists($className), $message);
+    }
+
+    public function getLoadClassNamespaceCollisionTests()
+    {
+        return array(
+            array(
+                array(
+                    'NamespaceCollision\\A' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/alpha',
+                    'NamespaceCollision\\A\\B' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/beta',
+                ),
+                'NamespaceCollision\A\Foo',
+                '->loadClass() loads NamespaceCollision\A\Foo from alpha.',
+            ),
+            array(
+                array(
+                    'NamespaceCollision\\A\\B' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/beta',
+                    'NamespaceCollision\\A' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/alpha',
+                ),
+                'NamespaceCollision\A\Bar',
+                '->loadClass() loads NamespaceCollision\A\Bar from alpha.',
+            ),
+            array(
+                array(
+                    'NamespaceCollision\\A' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/alpha',
+                    'NamespaceCollision\\A\\B' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/beta',
+                ),
+                'NamespaceCollision\A\B\Foo',
+                '->loadClass() loads NamespaceCollision\A\B\Foo from beta.',
+            ),
+            array(
+                array(
+                    'NamespaceCollision\\A\\B' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/beta',
+                    'NamespaceCollision\\A' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/alpha',
+                ),
+                'NamespaceCollision\A\B\Bar',
+                '->loadClass() loads NamespaceCollision\A\B\Bar from beta.',
+            ),
+        );
+    }
+
+    /**
+     * @dataProvider getLoadClassPrefixCollisionTests
+     */
+    public function testLoadClassPrefixCollision($prefixes, $className, $message)
+    {
+        $loader = new UniversalClassLoader();
+        $loader->registerPrefixes($prefixes);
+
+        $this->assertTrue($loader->loadClass($className));
+        $this->assertTrue(class_exists($className), $message);
+    }
+
+    public function getLoadClassPrefixCollisionTests()
+    {
+        return array(
+            array(
+                array(
+                    'PrefixCollision_A_' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/alpha',
+                    'PrefixCollision_A_B_' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/beta',
+                ),
+                'PrefixCollision_A_Foo',
+                '->loadClass() loads PrefixCollision_A_Foo from alpha.',
+            ),
+            array(
+                array(
+                    'PrefixCollision_A_B_' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/beta',
+                    'PrefixCollision_A_' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/alpha',
+                ),
+                'PrefixCollision_A_Bar',
+                '->loadClass() loads PrefixCollision_A_Bar from alpha.',
+            ),
+            array(
+                array(
+                    'PrefixCollision_A_' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/alpha',
+                    'PrefixCollision_A_B_' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/beta',
+                ),
+                'PrefixCollision_A_B_Foo',
+                '->loadClass() loads PrefixCollision_A_B_Foo from beta.',
+            ),
+            array(
+                array(
+                    'PrefixCollision_A_B_' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/beta',
+                    'PrefixCollision_A_' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures/alpha',
+                ),
+                'PrefixCollision_A_B_Bar',
+                '->loadClass() loads PrefixCollision_A_B_Bar from beta.',
+            ),
+        );
+    }
+}

UniversalClassLoader.php

@@ -0,0 +1,302 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\ClassLoader;
+
+/**
+ * UniversalClassLoader implements a "universal" autoloader for PHP 5.3.
+ *
+ * It is able to load classes that use either:
+ *
+ *  * The technical interoperability standards for PHP 5.3 namespaces and
+ *    class names (https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-0.md);
+ *
+ *  * The PEAR naming convention for classes (http://pear.php.net/).
+ *
+ * Classes from a sub-namespace or a sub-hierarchy of PEAR classes can be
+ * looked for in a list of locations to ease the vendoring of a sub-set of
+ * classes for large projects.
+ *
+ * Example usage:
+ *
+ *     $loader = new UniversalClassLoader();
+ *
+ *     // register classes with namespaces
+ *     $loader->registerNamespaces(array(
+ *         'Symfony\Component' => __DIR__.'/component',
+ *         'Symfony' => __DIR__.'/framework',
+ *         'Sensio' => array(__DIR__.'/src', __DIR__.'/vendor'),
+ *     ));
+ *
+ *     // register a library using the PEAR naming convention
+ *     $loader->registerPrefixes(array(
+ *         'Swift_' => __DIR__.'/Swift',
+ *     ));
+ *
+ *
+ *     // to enable searching the include path (e.g. for PEAR packages)
+ *     $loader->useIncludePath(true);
+ *
+ *     // activate the autoloader
+ *     $loader->register();
+ *
+ * In this example, if you try to use a class in the Symfony\Component
+ * namespace or one of its children (Symfony\Component\Console for instance),
+ * the autoloader will first look for the class under the component/
+ * directory, and it will then fallback to the framework/ directory if not
+ * found before giving up.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class UniversalClassLoader
+{
+    private $namespaces = array();
+    private $prefixes = array();
+    private $namespaceFallbacks = array();
+    private $prefixFallbacks = array();
+    private $useIncludePath = false;
+
+    /**
+     * Turns on searching the include for class files. Allows easy loading
+     * of installed PEAR packages.
+     *
+     * @param bool $useIncludePath
+     */
+    public function useIncludePath($useIncludePath)
+    {
+        $this->useIncludePath = (bool) $useIncludePath;
+    }
+
+    /**
+     * Can be used to check if the autoloader uses the include path to check
+     * for classes.
+     *
+     * @return bool
+     */
+    public function getUseIncludePath()
+    {
+        return $this->useIncludePath;
+    }
+
+    /**
+     * Gets the configured namespaces.
+     *
+     * @return array A hash with namespaces as keys and directories as values
+     */
+    public function getNamespaces()
+    {
+        return $this->namespaces;
+    }
+
+    /**
+     * Gets the configured class prefixes.
+     *
+     * @return array A hash with class prefixes as keys and directories as values
+     */
+    public function getPrefixes()
+    {
+        return $this->prefixes;
+    }
+
+    /**
+     * Gets the directory(ies) to use as a fallback for namespaces.
+     *
+     * @return array An array of directories
+     */
+    public function getNamespaceFallbacks()
+    {
+        return $this->namespaceFallbacks;
+    }
+
+    /**
+     * Gets the directory(ies) to use as a fallback for class prefixes.
+     *
+     * @return array An array of directories
+     */
+    public function getPrefixFallbacks()
+    {
+        return $this->prefixFallbacks;
+    }
+
+    /**
+     * Registers the directory to use as a fallback for namespaces.
+     *
+     * @param array $dirs An array of directories
+     */
+    public function registerNamespaceFallbacks(array $dirs)
+    {
+        $this->namespaceFallbacks = $dirs;
+    }
+
+    /**
+     * Registers a directory to use as a fallback for namespaces.
+     *
+     * @param string $dir A directory
+     */
+    public function registerNamespaceFallback($dir)
+    {
+        $this->namespaceFallbacks[] = $dir;
+    }
+
+    /**
+     * Registers directories to use as a fallback for class prefixes.
+     *
+     * @param array $dirs An array of directories
+     */
+    public function registerPrefixFallbacks(array $dirs)
+    {
+        $this->prefixFallbacks = $dirs;
+    }
+
+    /**
+     * Registers a directory to use as a fallback for class prefixes.
+     *
+     * @param string $dir A directory
+     */
+    public function registerPrefixFallback($dir)
+    {
+        $this->prefixFallbacks[] = $dir;
+    }
+
+    /**
+     * Registers an array of namespaces.
+     *
+     * @param array $namespaces An array of namespaces (namespaces as keys and locations as values)
+     */
+    public function registerNamespaces(array $namespaces)
+    {
+        foreach ($namespaces as $namespace => $locations) {
+            $this->namespaces[$namespace] = (array) $locations;
+        }
+    }
+
+    /**
+     * Registers a namespace.
+     *
+     * @param string       $namespace The namespace
+     * @param array|string $paths     The location(s) of the namespace
+     */
+    public function registerNamespace($namespace, $paths)
+    {
+        $this->namespaces[$namespace] = (array) $paths;
+    }
+
+    /**
+     * Registers an array of classes using the PEAR naming convention.
+     *
+     * @param array $classes An array of classes (prefixes as keys and locations as values)
+     */
+    public function registerPrefixes(array $classes)
+    {
+        foreach ($classes as $prefix => $locations) {
+            $this->prefixes[$prefix] = (array) $locations;
+        }
+    }
+
+    /**
+     * Registers a set of classes using the PEAR naming convention.
+     *
+     * @param string       $prefix The classes prefix
+     * @param array|string $paths  The location(s) of the classes
+     */
+    public function registerPrefix($prefix, $paths)
+    {
+        $this->prefixes[$prefix] = (array) $paths;
+    }
+
+    /**
+     * Registers this instance as an autoloader.
+     *
+     * @param bool $prepend Whether to prepend the autoloader or not
+     */
+    public function register($prepend = false)
+    {
+        spl_autoload_register(array($this, 'loadClass'), true, $prepend);
+    }
+
+    /**
+     * Loads the given class or interface.
+     *
+     * @param string $class The name of the class
+     *
+     * @return bool|null True, if loaded
+     */
+    public function loadClass($class)
+    {
+        if ($file = $this->findFile($class)) {
+            require $file;
+
+            return true;
+        }
+    }
+
+    /**
+     * Finds the path to the file where the class is defined.
+     *
+     * @param string $class The name of the class
+     *
+     * @return string|null The path, if found
+     */
+    public function findFile($class)
+    {
+        if (false !== $pos = strrpos($class, '\\')) {
+            // namespaced class name
+            $namespace = substr($class, 0, $pos);
+            $className = substr($class, $pos + 1);
+            $normalizedClass = str_replace('\\', DIRECTORY_SEPARATOR, $namespace).DIRECTORY_SEPARATOR.str_replace('_', DIRECTORY_SEPARATOR, $className).'.php';
+            foreach ($this->namespaces as $ns => $dirs) {
+                if (0 !== strpos($namespace, $ns)) {
+                    continue;
+                }
+
+                foreach ($dirs as $dir) {
+                    $file = $dir.DIRECTORY_SEPARATOR.$normalizedClass;
+                    if (is_file($file)) {
+                        return $file;
+                    }
+                }
+            }
+
+            foreach ($this->namespaceFallbacks as $dir) {
+                $file = $dir.DIRECTORY_SEPARATOR.$normalizedClass;
+                if (is_file($file)) {
+                    return $file;
+                }
+            }
+        } else {
+            // PEAR-like class name
+            $normalizedClass = str_replace('_', DIRECTORY_SEPARATOR, $class).'.php';
+            foreach ($this->prefixes as $prefix => $dirs) {
+                if (0 !== strpos($class, $prefix)) {
+                    continue;
+                }
+
+                foreach ($dirs as $dir) {
+                    $file = $dir.DIRECTORY_SEPARATOR.$normalizedClass;
+                    if (is_file($file)) {
+                        return $file;
+                    }
+                }
+            }
+
+            foreach ($this->prefixFallbacks as $dir) {
+                $file = $dir.DIRECTORY_SEPARATOR.$normalizedClass;
+                if (is_file($file)) {
+                    return $file;
+                }
+            }
+        }
+
+        if ($this->useIncludePath && $file = stream_resolve_include_path($normalizedClass)) {
+            return $file;
+        }
+    }
+}

WinCacheClassLoader.php

@@ -16,10 +16,12 @@ namespace Symfony\Component\ClassLoader;
  *
  * It expects an object implementing a findFile method to find the file. This
  * allow using it as a wrapper around the other loaders of the component (the
- * ClassLoader for instance) but also around any other autoloaders following
- * this convention (the Composer one for instance).
+ * ClassLoader and the UniversalClassLoader for instance) but also around any
+ * other autoloaders following this convention (the Composer one for instance).
  *
  *     // with a Symfony autoloader
+ *     use Symfony\Component\ClassLoader\ClassLoader;
+ *
  *     $loader = new ClassLoader();
  *     $loader->addPrefix('Symfony\Component', __DIR__.'/component');
  *     $loader->addPrefix('Symfony',           __DIR__.'/framework');
@@ -121,8 +123,10 @@ class WinCacheClassLoader
      */
     public function findFile($class)
     {
-        if (false === $file = wincache_ucache_get($this->prefix.$class)) {
-            wincache_ucache_set($this->prefix.$class, $file = $this->decorated->findFile($class), 0);
+        $file = wincache_ucache_get($this->prefix.$class, $success);
+
+        if (!$success) {
+            wincache_ucache_set($this->prefix.$class, $file = $this->decorated->findFile($class) ?: null, 0);
         }
 
         return $file;

XcacheClassLoader.php

@@ -16,10 +16,12 @@ namespace Symfony\Component\ClassLoader;
  *
  * It expects an object implementing a findFile method to find the file. This
  * allows using it as a wrapper around the other loaders of the component (the
- * ClassLoader for instance) but also around any other autoloaders following
- * this convention (the Composer one for instance).
+ * ClassLoader and the UniversalClassLoader for instance) but also around any
+ * other autoloaders following this convention (the Composer one for instance).
  *
  *     // with a Symfony autoloader
+ *     use Symfony\Component\ClassLoader\ClassLoader;
+ *
  *     $loader = new ClassLoader();
  *     $loader->addPrefix('Symfony\Component', __DIR__.'/component');
  *     $loader->addPrefix('Symfony',           __DIR__.'/framework');
@@ -124,7 +126,7 @@ class XcacheClassLoader
         if (xcache_isset($this->prefix.$class)) {
             $file = xcache_get($this->prefix.$class);
         } else {
-            $file = $this->decorated->findFile($class);
+            $file = $this->decorated->findFile($class) ?: null;
             xcache_set($this->prefix.$class, $file);
         }
 

composer.json

@@ -17,20 +17,22 @@
     ],
     "minimum-stability": "dev",
     "require": {
-        "php": ">=5.5.9"
+        "php": ">=5.3.3",
+        "symfony/polyfill-apcu": "~1.1"
     },
     "require-dev": {
-        "symfony/finder": "~2.8|~3.0"
+        "symfony/finder": "~2.0,>=2.0.5"
     },
     "autoload": {
-        "psr-4": { "Symfony\\Component\\ClassLoader\\": "" },
+        "psr-0": { "Symfony\\Component\\ClassLoader\\": "" },
         "exclude-from-classmap": [
             "/Tests/"
         ]
     },
+    "target-dir": "Symfony/Component/ClassLoader",
     "extra": {
         "branch-alias": {
-            "dev-master": "3.0-dev"
+            "dev-master": "2.3-dev"
         }
     }
 }