Update README.md

replace composer install by composer require

Exception/FatalErrorException.php

@@ -35,8 +35,7 @@ class FatalErrorException extends \ErrorException
 
             $this->setTrace($trace);
         } elseif (null !== $traceOffset) {
-            if (\function_exists('xdebug_get_function_stack')) {
-                $trace = xdebug_get_function_stack();
+            if (\function_exists('xdebug_get_function_stack') && $trace = @xdebug_get_function_stack()) {
                 if (0 < $traceOffset) {
                     array_splice($trace, -$traceOffset);
                 }

Exception/FatalThrowableError.php

@@ -26,7 +26,7 @@ class FatalThrowableError extends FatalErrorException
 
     public function __construct(\Throwable $e)
     {
-        $this->originalClassName = get_debug_type($e);
+        $this->originalClassName = \get_class($e);
 
         if ($e instanceof \ParseError) {
             $severity = \E_PARSE;

Exception/FlattenException.php

@@ -67,7 +67,7 @@ class FlattenException
         $e->setStatusCode($statusCode);
         $e->setHeaders($headers);
         $e->setTraceFromThrowable($exception);
-        $e->setClass($exception instanceof FatalThrowableError ? $exception->getOriginalClassName() : get_debug_type($exception));
+        $e->setClass($exception instanceof FatalThrowableError ? $exception->getOriginalClassName() : \get_class($exception));
         $e->setFile($exception->getFile());
         $e->setLine($exception->getLine());
 

FatalErrorHandler/UndefinedMethodFatalErrorHandler.php

@@ -40,7 +40,7 @@ class UndefinedMethodFatalErrorHandler implements FatalErrorHandlerInterface
 
         $message = sprintf('Attempted to call an undefined method named "%s" of class "%s".', $methodName, $className);
 
-        if (!class_exists($className) || null === $methods = get_class_methods($className)) {
+        if ('' === $methodName || !class_exists($className) || null === $methods = get_class_methods($className)) {
             // failed to get the class or its methods on which an unknown method was called (for example on an anonymous class)
             return new UndefinedMethodException($message, $exception);
         }

README.md

@@ -12,7 +12,7 @@ Getting Started
 ---------------
 
 ```
-$ composer install symfony/debug
+$ composer require symfony/debug
 ```
 
 ```php
@@ -24,7 +24,7 @@ Debug::enable();
 Resources
 ---------
 
-  * [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)
+ * [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/FatalErrorHandler/UndefinedMethodFatalErrorHandlerTest.php

@@ -48,6 +48,15 @@ class UndefinedMethodFatalErrorHandlerTest extends TestCase
                 ],
                 'Attempted to call an undefined method named "what" of class "SplObjectStorage".',
             ],
+            [
+                [
+                    'type' => 1,
+                    'line' => 12,
+                    'file' => 'foo.php',
+                    'message' => 'Call to undefined method SplObjectStorage::()',
+                ],
+                'Attempted to call an undefined method named "" of class "SplObjectStorage".',
+            ],
             [
                 [
                     'type' => 1,

Tests/phpt/exception_rethrown.phpt

@@ -14,7 +14,7 @@ require $vendor.'/vendor/autoload.php';
 if (true) {
     class TestLogger extends \Psr\Log\AbstractLogger
     {
-        public function log($level, $message, array $context = [])
+        public function log($level, $message, array $context = []): void
         {
             echo $message, "\n";
         }

composer.json

@@ -17,8 +17,7 @@
     ],
     "require": {
         "php": ">=7.1.3",
-        "psr/log": "~1.0",
-        "symfony/polyfill-php80": "^1.15"
+        "psr/log": "^1|^2|^3"
     },
     "conflict": {
         "symfony/http-kernel": "<3.4"