Abstract Singleton Class with Params

<?php
abstract class singleton_array_id_abstract
{
    private static $Instance = array();
    protected static $connID = NULL;

    protected function __construct()
    {
    }

    public static function getInstance($connID=1)
    {
        self::$connID = $connID;
        $ClassName = get_called_class();
        if(!isset(self::$Instance[$connID][$ClassName]))
        {
            self::$Instance[$connID][$ClassName] = new $ClassName();
        }
        $ObjInstance = self::$Instance[$connID][$ClassName];
        return $ObjInstance;
    }

    final private function __clone(){}

    final private function __wakeup(){}

    final public function get_connID()
    {
            return self::$connID;
        }
}
# class db extends singleton_array_id_abstract {
#   protected function __construct() {
#       $this->ID = $this->get_connID();
#   }
# .....
# }

# $db = db::getInstance(SERVER_ID);
?>