php ajax请求和返回

        define('NOW_TIME',      $_SERVER['REQUEST_TIME']);
        define('REQUEST_METHOD',$_SERVER['REQUEST_METHOD']);
        define('IS_GET',        REQUEST_METHOD =='GET' ? true : false);
        define('IS_POST',       REQUEST_METHOD =='POST' ? true : false);
        define('IS_PUT',        REQUEST_METHOD =='PUT' ? true : false);
        define('IS_DELETE',     REQUEST_METHOD =='DELETE' ? true : false);
        define('IS_AJAX',       ((isset($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest') || !empty($_POST[C('VAR_AJAX_SUBMIT')]) || !empty($_GET[C('VAR_AJAX_SUBMIT')])) ? true : false);

function ajaxReturn($code, $msg = '', $data = array(), $redirect = '') {
    $data = array(
        'code' => $code,
        'message' => $msg,
        'data' => $data,
        'redirect' => $redirect
    );
    header('Content-Type:application/json; charset=utf-8');
    exit(jsonEncode($data));
}