요청이 XMLHttpRequest 객체에서 오는지 여부를 확인하는 zf 메서드

/*
* * Is the request a Javascript XMLHttpRequest?
* * Should work with Prototype/Script.aculo.us, possibly others.
* * @return boolean
*/
public function isXmlHttpRequest() {
    return (
    $this->getHeader('X_REQUESTED_WITH') == 'XMLHttpRequest');
}