Deprecate returning non-string values from a user output handler (#18932)

https://wiki.php.net/rfc/deprecations_php_8_4

tests/output/bug60768.phpt

@@ -5,7 +5,7 @@ Bug #60768 Output buffer not discarded
 
 global $storage;
 
-ob_start(function($buffer) use (&$storage) { $storage .= $buffer; }, 20);
+ob_start(function($buffer) use (&$storage) { $storage .= $buffer; return ''; }, 20);
 
 echo str_repeat("0", 20); // fill in the buffer
 

tests/output/ob_start_basic_002.phpt

@@ -35,19 +35,24 @@ foreach ($callbacks as $callback) {
 }
 
 ?>
---EXPECT--
+--EXPECTF--
 --> Use callback 'return_empty_string':
 
 
 --> Use callback 'return_false':
+
+Deprecated: ob_end_flush(): Returning a non-string result from user output handler return_false is deprecated in %s on line %d
 My output.
 
 --> Use callback 'return_null':
 
+Deprecated: ob_end_flush(): Returning a non-string result from user output handler return_null is deprecated in %s on line %d
+
 
 --> Use callback 'return_string':
 I stole your output.
 
 --> Use callback 'return_zero':
-0
 
+Deprecated: ob_end_flush(): Returning a non-string result from user output handler return_zero is deprecated in %s on line %d
+0

tests/output/ob_start_callback_bad_return/exception_handler.phpt

@@ -0,0 +1,147 @@
+--TEST--
+ob_start(): Check behaviour with deprecation converted to exception
+--FILE--
+<?php
+
+class NotStringable {
+    public function __construct(public string $val) {}
+}
+class IsStringable {
+    public function __construct(public string $val) {}
+    public function __toString() {
+        return __CLASS__ . ": " . $this->val;
+    }
+}
+
+$log = [];
+
+set_error_handler(function (int $errno, string $errstr, string $errfile, int $errline) {
+    throw new \ErrorException($errstr, 0, $errno, $errfile, $errline);
+});
+
+function return_null($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return null;
+}
+
+function return_false($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return false;
+}
+
+function return_true($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return true;
+}
+
+function return_zero($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return 0;
+}
+
+function return_non_stringable($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return new NotStringable($string);
+}
+
+function return_stringable($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return new IsStringable($string);
+}
+
+$cases = [
+    'return_null',
+    'return_false',
+    'return_true',
+    'return_zero',
+    'return_non_stringable',
+    'return_stringable',
+];
+foreach ($cases as $case) {
+    $log = [];
+    echo "\n\nTesting: $case\n";
+    ob_start($case);
+    echo "Inside of $case\n";
+    try {
+        ob_end_flush();
+    } catch (\ErrorException $e) {
+        echo $e . "\n";
+    }
+    echo "\nEnd of $case, log was:\n";
+    echo implode("\n", $log);
+}
+
+?>
+--EXPECTF--
+Testing: return_null
+ErrorException: ob_end_flush(): Returning a non-string result from user output handler return_null is deprecated in %s:%d
+Stack trace:
+#0 [internal function]: {closure:%s:%d}(8192, 'ob_end_flush():...', %s, %d)
+#1 %s(%d): ob_end_flush()
+#2 {main}
+
+End of return_null, log was:
+return_null: <<<Inside of return_null
+>>>
+
+Testing: return_false
+Inside of return_false
+ErrorException: ob_end_flush(): Returning a non-string result from user output handler return_false is deprecated in %s:%d
+Stack trace:
+#0 [internal function]: {closure:%s:%d}(8192, 'ob_end_flush():...', %s, %d)
+#1 %s(%d): ob_end_flush()
+#2 {main}
+
+End of return_false, log was:
+return_false: <<<Inside of return_false
+>>>
+
+Testing: return_true
+ErrorException: ob_end_flush(): Returning a non-string result from user output handler return_true is deprecated in %s:%d
+Stack trace:
+#0 [internal function]: {closure:%s:%d}(8192, 'ob_end_flush():...', %s, %d)
+#1 %s(%d): ob_end_flush()
+#2 {main}
+
+End of return_true, log was:
+return_true: <<<Inside of return_true
+>>>
+
+Testing: return_zero
+0ErrorException: ob_end_flush(): Returning a non-string result from user output handler return_zero is deprecated in %s:%d
+Stack trace:
+#0 [internal function]: {closure:%s:%d}(8192, 'ob_end_flush():...', %s, %d)
+#1 %s(%d): ob_end_flush()
+#2 {main}
+
+End of return_zero, log was:
+return_zero: <<<Inside of return_zero
+>>>
+
+Testing: return_non_stringable
+ErrorException: ob_end_flush(): Returning a non-string result from user output handler return_non_stringable is deprecated in %s:%d
+Stack trace:
+#0 [internal function]: {closure:%s:%d}(8192, 'ob_end_flush():...', %s, 69)
+#1 %s(%d): ob_end_flush()
+#2 {main}
+
+End of return_non_stringable, log was:
+return_non_stringable: <<<Inside of return_non_stringable
+>>>
+
+Testing: return_stringable
+ErrorException: ob_end_flush(): Returning a non-string result from user output handler return_stringable is deprecated in %s:%d
+Stack trace:
+#0 [internal function]: {closure:%s:%d}(8192, 'ob_end_flush():...', %s, 69)
+#1 %s(%d): ob_end_flush()
+#2 {main}
+
+End of return_stringable, log was:
+return_stringable: <<<Inside of return_stringable
+>>>

tests/output/ob_start_callback_bad_return/exception_handler_nested.phpt

@@ -0,0 +1,143 @@
+--TEST--
+ob_start(): Check behaviour with deprecation converted to exception
+--FILE--
+<?php
+
+class NotStringable {
+    public function __construct(public string $val) {}
+}
+class IsStringable {
+    public function __construct(public string $val) {}
+    public function __toString() {
+        return __CLASS__ . ": " . $this->val;
+    }
+}
+
+$log = [];
+
+set_error_handler(function (int $errno, string $errstr, string $errfile, int $errline) {
+    throw new \ErrorException($errstr, 0, $errno, $errfile, $errline);
+});
+
+function return_null($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return null;
+}
+
+function return_false($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return false;
+}
+
+function return_true($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return true;
+}
+
+function return_zero($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return 0;
+}
+
+function return_non_stringable($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return new NotStringable($string);
+}
+
+function return_stringable($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return new IsStringable($string);
+}
+
+ob_start('return_null');
+ob_start('return_false');
+ob_start('return_true');
+ob_start('return_zero');
+ob_start('return_non_stringable');
+ob_start('return_stringable');
+
+echo "In all of them\n\n";
+try {
+    ob_end_flush();
+} catch (\ErrorException $e) {
+    echo $e->getMessage() . "\n";
+}
+echo "Ended return_stringable handler\n\n";
+
+try {
+    ob_end_flush();
+} catch (\ErrorException $e) {
+    echo $e->getMessage() . "\n";
+}
+echo "Ended return_non_stringable handler\n\n";
+
+try {
+    ob_end_flush();
+} catch (\ErrorException $e) {
+    echo $e->getMessage() . "\n";
+}
+echo "Ended return_zero handler\n\n";
+
+try {
+    ob_end_flush();
+} catch (\ErrorException $e) {
+    echo $e->getMessage() . "\n";
+}
+echo "Ended return_true handler\n\n";
+
+try {
+    ob_end_flush();
+} catch (\ErrorException $e) {
+    echo $e->getMessage() . "\n";
+}
+echo "Ended return_false handler\n\n";
+
+try {
+    ob_end_flush();
+} catch (\ErrorException $e) {
+    echo $e->getMessage() . "\n";
+}
+echo "Ended return_null handler\n\n";
+
+echo "All handlers are over\n\n";
+echo implode("\n", $log);
+
+?>
+--EXPECT--
+ob_end_flush(): Returning a non-string result from user output handler return_null is deprecated
+Ended return_null handler
+
+All handlers are over
+
+return_stringable: <<<In all of them
+
+>>>
+return_non_stringable: <<<ob_end_flush(): Returning a non-string result from user output handler return_stringable is deprecated
+Ended return_stringable handler
+
+>>>
+return_zero: <<<ob_end_flush(): Returning a non-string result from user output handler return_non_stringable is deprecated
+Ended return_non_stringable handler
+
+>>>
+return_true: <<<0ob_end_flush(): Returning a non-string result from user output handler return_zero is deprecated
+Ended return_zero handler
+
+>>>
+return_false: <<<ob_end_flush(): Returning a non-string result from user output handler return_true is deprecated
+Ended return_true handler
+
+>>>
+return_null: <<<ob_end_flush(): Returning a non-string result from user output handler return_true is deprecated
+Ended return_true handler
+
+ob_end_flush(): Returning a non-string result from user output handler return_false is deprecated
+Ended return_false handler
+
+>>>

tests/output/ob_start_callback_bad_return/handler_false_removed.phpt

@@ -0,0 +1,23 @@
+--TEST--
+ob_start(): Check behaviour with deprecation when OOM triggers handler removal (handler returns false)
+--INI--
+memory_limit=2M
+--FILE--
+<?php
+
+ob_start(function() {
+    // We are out of memory, now trigger a deprecation
+    return false;
+});
+
+$a = [];
+// trigger OOM in a resize operation
+while (1) {
+    $a[] = 1;
+}
+
+?>
+--EXPECTF--
+Deprecated: main(): Returning a non-string result from user output handler {closure:%s:%d} is deprecated in %s on line %d
+
+Fatal error: Allowed memory size of %d bytes exhausted%s(tried to allocate %d bytes) in %s on line %d

tests/output/ob_start_callback_bad_return/handler_is_stringable_removed.phpt

@@ -0,0 +1,30 @@
+--TEST--
+ob_start(): Check behaviour with deprecation when OOM triggers handler removal (handler returns stringable object)
+--INI--
+memory_limit=2M
+--FILE--
+<?php
+
+class IsStringable {
+    public function __construct(public string $val) {}
+    public function __toString() {
+        return __CLASS__ . ": " . $this->val;
+    }
+}
+
+ob_start(function() {
+    // We are out of memory, now trigger a deprecation
+    return new IsStringable("");
+});
+
+$a = [];
+// trigger OOM in a resize operation
+while (1) {
+    $a[] = 1;
+}
+
+?>
+--EXPECTF--
+Deprecated: main(): Returning a non-string result from user output handler {closure:%s:%d} is deprecated in %s on line %d
+
+Fatal error: Allowed memory size of %d bytes exhausted%s(tried to allocate %d bytes) in %s on line %d

tests/output/ob_start_callback_bad_return/handler_non_stringable_removed.phpt

@@ -0,0 +1,32 @@
+--TEST--
+ob_start(): Check behaviour with deprecation when OOM triggers handler removal (handler returns non-stringable object)
+--INI--
+memory_limit=2M
+--FILE--
+<?php
+
+class NotStringable {
+    public function __construct(public string $val) {}
+}
+
+ob_start(function() {
+    // We are out of memory, now trigger a deprecation
+    return new NotStringable("");
+});
+
+$a = [];
+// trigger OOM in a resize operation
+while (1) {
+    $a[] = 1;
+}
+
+?>
+--EXPECTF--
+Deprecated: main(): Returning a non-string result from user output handler {closure:%s:%d} is deprecated in %s on line %d
+
+Fatal error: Allowed memory size of %d bytes exhausted%s(tried to allocate %d bytes) in %s on line %d
+
+Fatal error: Uncaught Error: Object of class NotStringable could not be converted to string in %s:%d
+Stack trace:
+#0 {main}
+  thrown in %s on line %d

tests/output/ob_start_callback_bad_return/handler_true_removed.phpt

@@ -0,0 +1,23 @@
+--TEST--
+ob_start(): Check behaviour with deprecation when OOM triggers handler removal (handler returns true)
+--INI--
+memory_limit=2M
+--FILE--
+<?php
+
+ob_start(function() {
+    // We are out of memory, now trigger a deprecation
+    return true;
+});
+
+$a = [];
+// trigger OOM in a resize operation
+while (1) {
+    $a[] = 1;
+}
+
+?>
+--EXPECTF--
+Deprecated: main(): Returning a non-string result from user output handler {closure:%s:%d} is deprecated in %s on line %d
+
+Fatal error: Allowed memory size of %d bytes exhausted%s(tried to allocate %d bytes) in %s on line %d

tests/output/ob_start_callback_bad_return/handler_zero_removed.phpt

@@ -0,0 +1,23 @@
+--TEST--
+ob_start(): Check behaviour with deprecation when OOM triggers handler removal (handler returns zero)
+--INI--
+memory_limit=2M
+--FILE--
+<?php
+
+ob_start(function() {
+    // We are out of memory, now trigger a deprecation
+    return 0;
+});
+
+$a = [];
+// trigger OOM in a resize operation
+while (1) {
+    $a[] = 1;
+}
+
+?>
+--EXPECTF--
+Deprecated: main(): Returning a non-string result from user output handler {closure:%s:%d} is deprecated in %s on line %d
+
+Fatal error: Allowed memory size of %d bytes exhausted%s(tried to allocate %d bytes) in %s on line %d

tests/output/ob_start_callback_bad_return/multiple_handlers.phpt

@@ -0,0 +1,89 @@
+--TEST--
+ob_start(): Check behaviour with multiple nested handlers with had return values
+--FILE--
+<?php
+
+$log = [];
+
+function return_given_string($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return $string;
+}
+
+function return_empty_string($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return "";
+}
+
+function return_false($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return false;
+}
+
+function return_true($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return true;
+}
+
+function return_null($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return null;
+}
+
+function return_string($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return "I stole your output.";
+}
+
+function return_zero($string) {
+    global $log;
+    $log[] = __FUNCTION__ . ": <<<" . $string . ">>>";
+    return 0;
+}
+
+ob_start('return_given_string');
+ob_start('return_empty_string');
+ob_start('return_false');
+ob_start('return_true');
+ob_start('return_null');
+ob_start('return_string');
+ob_start('return_zero');
+
+echo "Testing...";
+
+ob_end_flush();
+ob_end_flush();
+ob_end_flush();
+ob_end_flush();
+ob_end_flush();
+ob_end_flush();
+ob_end_flush();
+
+echo "\n\nLog:\n";
+echo implode("\n", $log);
+?>
+--EXPECTF--
+Log:
+return_zero: <<<Testing...>>>
+return_string: <<<
+Deprecated: ob_end_flush(): Returning a non-string result from user output handler return_zero is deprecated in %s on line %d
+0>>>
+return_null: <<<I stole your output.>>>
+return_true: <<<
+Deprecated: ob_end_flush(): Returning a non-string result from user output handler return_null is deprecated in %s on line %d
+>>>
+return_false: <<<
+Deprecated: ob_end_flush(): Returning a non-string result from user output handler return_true is deprecated in %s on line %d
+>>>
+return_empty_string: <<<
+Deprecated: ob_end_flush(): Returning a non-string result from user output handler return_false is deprecated in %s on line %d
+
+Deprecated: ob_end_flush(): Returning a non-string result from user output handler return_true is deprecated in %s on line %d
+>>>
+return_given_string: <<<>>>