Question

How would one create a Singleton class using PHP5 classes?

Answer 1

/**  * Singleton class  *  */ final class UserFactory {     private static $inst = null;      // Prevent cloning and de-serializing     private function __clone(){}     private function __wakeup(){}       /**      * Call this method to get singleton      *      * @return UserFactory      */     public static function Instance()     {         if ($inst === null) {             $inst = new UserFactory();         }         return $inst;     }          /**      * Private ctor so nobody else can instantiate it      *      */     private function __construct()     {              } } 

To use:

$fact = UserFactory::Instance(); $fact2 = UserFactory::Instance(); 

$fact == $fact2;

But:

$fact = new UserFactory() 

Throws an error.

See http://php.net/manual/en/language.variables.scope.php#language.variables.scope.static to understand static variable scopes and why setting static $inst = null; works.