src/Mage/Core/Controller/Request/Http.php
public function isAjax()
    {
        if ($this->isXmlHttpRequest()) {
            return true;
        }
        if ($this->getParam('ajax') || $this->getParam('isAjax')) {
            return true;
        }
        return false;
    }
public function isAjax()
    {
        if ($this->isXmlHttpRequest()) {
            return true;
        }
        if ($this->getParam('ajax') || $this->getParam('isAjax')) {
            return true;
        }
        return false;
    }
public function isAjax ( ) { if ( $ this -> isXmlHttpRequest ( ) ) { return true ; } if ( $ this -> getParam ( 'ajax' ) || $ this -> getParam ( 'isAjax' ) ) { return true ; } return false ; }
Check is Request from AJAX

@return boolean
Check is Request from AJAX