/**
  * Returns an array of all the enabled extensions available
  *
  * @return array
  */
 public function listInstalledHandles()
 {
     if (is_null(self::$_enabled_extensions)) {
         self::$_enabled_extensions = Symphony::Database()->fetchCol('name', "SELECT `name` FROM `tbl_extensions` WHERE `status` = 'enabled'");
     }
     return self::$_enabled_extensions;
 }