ajax 返回值方法（php）

<?phpfunction msg_error($state, $msg) {    if(!empty($_REQUEST['callback'])) {        $callback = $_REQUEST['callback'];        $callback = preg_replace(array('/</', '/>/', '/"/', '/\'/',  '/\+/', '/\\\\/', '/\//'), array('&lt;', '&gt;', '', '', '', '', ''), $callback);    }    $a = array(        'state' => $state,        'msg' => $msg,    );    $ret = json_encode($a);    if(!empty($callback)) $ret = sprintf("%s(%s)", $callback, $ret);    header("Content-type: application/json");    echo $ret;    exit;}