Question

The singleton is explained here: http://en.wikipedia.org/wiki/Singleton_pattern#PHP_5. I want to use the singleton class as a superclass, and extend it in other classes that are supposed to be singletons. The problem is, the superclass makes an instance of itself, not the subclass. Any idea how I can make the Superclass create an instance of the Subclass?

 class Singleton {      // object instance     private static $instance;      protected function __construct() { }     public function __clone() { }     public function __wakeup() { }      protected static function getInstance() {         if (!self::$instance instanceof self) {              self::$instance = new self;              if(self::$instance instanceof Singleton)                 echo 'made Singleton object<br />';              if(self::$instance instanceof Text)                 echo 'made Test object<br />';         }         return self::$instance;     }  }   class Test extends Singleton {      private static $values=array();      protected function load(){         $this->values['a-value'] = 'test';     }      public static function get($arg){         if(count(self::getInstance()->values)===0)             self::getInstance()->load();          if(isset(self::getInstance()->values[$arg]))             return self::getInstance()->values[$arg];          return false;     } } 

Answer 1

This is a limitation of PHP – a parent class cannot determine the name of a subclass on which its methods are statically called.

PHP 5.3 now has support for late static bindings, which will let you do what you need to, but it will be a while before that is widely available. See some information here

There are several similar questions on here which might be worth reading for possible workarounds, for example this one