note 86133 modified in function.get-class by danbrown

The code just worked fine with PHP 5.3.
Thanks to you it could be rebuild to work with earlier versions of PHP 5.

I just changed the 'static' to 'self' and die() to an Exception.

<?php
// This one extends Singleton with proper class name
class someSingleton extends Singleton {
    public static function getInstance() {
        parent::$__CLASS__ = __CLASS__;
        parent::getInstance();
    }
}
// This one does the logic
abstract class Singleton {
    protected static $__CLASS__ = __CLASS__;
    protected static $instance = null;

    protected function __construct() {}   
    abstract protected function init();
   
    /**
     * Gets an instance of this singleton. If no instance exists, a new instance is created and returned.
     * If one does exist, then the existing instance is returned.
     */
    public static function getInstance() {       
        $class = self::getClass();
       
        if (self::$instance === null) {
            self::$instance = new $class();
            self::$instance->init();
        }
       
        return self::$instance;
    }
   
    /**
     * Returns the classname of the child class extending this class
     *
     * @return string The class name
     */
    private static function getClass() {
        $implementing_class = self::$__CLASS__;
        $original_class = __CLASS__;

        if ($implementing_class === $original_class)
            throw new Exception("You MUST provide a <code>protected static \$__CLASS__ = __CLASS__;</code> statement in your Singleton-class!");
       
        return $implementing_class;
    }
}
?>

--was--
The code just worked fine with PHP 5.3.
Thanks to you it could be rebuild to work with earlier versions of PHP 5.

I just changed the 'static' to 'self' and die() to an Exception.

<?php
// This one extends Singleton with proper class name
class someSingleton extends Singleton {
    public static function getInstance() {
        parent::$__CLASS__ = __CLASS__;
        parent::getInstance();
    }
}
// This one does the logic
abstract class Singleton {
    protected static $__CLASS__ = __CLASS__;
    protected static $instance = null;

    protected function __construct() {}   
    abstract protected function init();
   
    /**
     * Gets an instance of this singleton. If no instance exists, a new instance is created and returned.
     * If one does exist, then the existing instance is returned.
     */
    public static function getInstance() {       
        $class = self::getClass();
       
        if (self::$instance === null) {
            self::$instance = new $class();
            self::$instance->init();
        }
       
        return self::$instance;
    }
   
    /**
     * Returns the classname of the child class extending this class
     *
     * @return string The class name
     */
    private static function getClass() {
        $implementing_class = self::$__CLASS__;
        $original_class = __CLASS__;

        if ($implementing_class === $original_class)
            throw new Exception("You MUST provide a <code>protected static \$__CLASS__ = __CLASS__;</code> statement in your Singleton-class!");
       
        return $implementing_class;
    }
}

http://php.net/manual/en/function.get-class.php