/**
* This implements the 'singleton' design pattern
*
* @param integer Options to initialize with this instance. See rcube::INIT_WITH_* constants
*
* @return rcube The one and only instance
*/
static function get_instance($mode = 0)
{
if (!self::$instance) {
self::$instance = new rcube();
self::$instance->init($mode);
}
return self::$instance;
}