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<?php class Singleton { /** * @var Singleton The reference to *Singleton* instance of this class */ private static $instance; /** * Returns the *Singleton* instance of this class. * * @return Singleton The *Singleton* instance. */ public static function getInstance() { if (null === self::$instance) { self::$instance = new static(); } return self::$instance; } /** * Protected constructor to prevent creating a new instance of the * *Singleton* via the `new` operator from outside of this class. */ protected function __construct() { } /** * Private clone method to prevent cloning of the instance of the * *Singleton* instance. * * @return void */ private function __clone() { } /** * Private unserialize method to prevent unserializing of the *Singleton* * instance. * * @return void */ private function __wakeup() { } } class SingletonChild extends Singleton { } $obj = Singleton::getInstance(); var_dump($obj === Singleton::getInstance()); // bool(true) $anotherObj = SingletonChild::getInstance(); var_dump($anotherObj === Singleton::getInstance()); // bool(false) var_dump($anotherObj === SingletonChild::getInstance()); // bool(true)
Output for 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
Warning: The magic method Singleton::__wakeup() must have public visibility in /in/OU2TB on line 48 bool(true) bool(true) bool(true)
Output for 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33
bool(true) bool(true) bool(true)
Output for 5.1.0 - 5.1.6, 5.2.0 - 5.2.17
Parse error: syntax error, unexpected T_STATIC, expecting T_STRING or T_VARIABLE or '$' in /in/OU2TB on line 18
Process exited with code 255.
Output for 5.0.0 - 5.0.5
Parse error: parse error, unexpected T_STATIC, expecting T_STRING or T_VARIABLE or '$' in /in/OU2TB on line 18
Process exited with code 255.
Output for 4.4.2 - 4.4.9
Parse error: syntax error, unexpected T_STRING, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or '}' in /in/OU2TB on line 8
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1
Parse error: parse error, unexpected T_STRING, expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or '}' in /in/OU2TB on line 8
Process exited with code 255.
Output for 4.3.2 - 4.3.4
Parse error: parse error, expecting `T_OLD_FUNCTION' or `T_FUNCTION' or `T_VAR' or `'}'' in /in/OU2TB on line 8
Process exited with code 255.

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