singleton.pattern.php

<?php
/**
 * Abstract Class for Singleton Pattern management.
 * @author Frédéric Delorme<[email protected]>
 * @version 1.0
 * @copyright 2010/08/15
 *
 */
abstract class Singleton 
{
	/**
	 * INstances array maintained by the class.
	 * @var Array
	 */
    private static $_instances=array();
    
    /**
     * To be implemented in all childs of this pattern.
     * method must call parrent::getSingletonInstance(__CLASS__);
     * to return to Singleton manager the class name to be instanciate.
     */
 	public abstract static function getInstance(); 
 	
 	/**
 	 * return unique instance of the class <code>$className</code>.
 	 * @param string $className
 	 */
    public static function getSingletonInstance($className){
    	__debug("Return an instance of the needed class $className","getSingletonInstance",__CLASS__);
        $classNameString = "".$className;
        if (!isset(self::$_instances[$classNameString])){
            self::$_instances[$classNameString] = new $classNameString;
        }
 		//echo "<pre>instances:{".print_r(self::$_instances,true)."}</pre>";
        return self::$_instances[$classNameString];
    }
 
    //TODO Do not allow an explicit call of the constructor: $v = new Singleton();
    //final private function __construct() { }
 
    // Do not allow the clone operation: $x = clone $v;
    final private function __clone() { }
}
?>

a very simple Singleton pattern adapted from existing sample class from http://www.php.net/manual/en/language.oop5.patterns.php#90360 :
How to use:
class MySingletonizedClass extends Singleton{
// my stuff
// ...
// ...
public static function getInstance(){
parent::getSingletonInstance(CLASS);
}
}

and just do a:

$msc = MySingletonizedClass::getInstance();

and you will get the singleton instance ;)