<?php class Singleton { /** * @var Singleton The reference to *Singleton* instance of this class */ protected static $instance; /** * Returns the *Singleton* instance of this class. * * @return Singleton The *Singleton* instance. */ public static function getInstance() { if (null === static::$instance) { static::$instance = new static(); } return static::$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)
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