private static function _checkCallback($cls, $callback, $context)
    {
        self::_initiateCallbacks($cls);
        foreach (self::$_callbacks[$cls][$callback] as $func) {
            if (!call_user_func(array($context, $func))) {
                return false;
            }
        }
        return true;
    }
private static function _checkCallback($cls, $callback, $context)
    {
        self::_initiateCallbacks($cls);
        foreach (self::$_callbacks[$cls][$callback] as $func) {
            if (!call_user_func(array($context, $func))) {
                return false;
            }
        }
        return true;
    }
private static function _checkCallback ( $ cls , $ callback , $ context ) { self :: _initiateCallbacks ( $ cls ) ; foreach ( self :: $ _callbacks [ $ cls ] [ $ callback ] as $ func ) { if ( ! call_user_func ( array ( $ context , $ func ) ) ) { return false ; } } return true ; }
Check if a callback exists

@param string $cls      class
@param string $callback callback
@param mixed  $context  context (instance)

@return exist or not
Check if a callback exists