出现400错误怎么回事?

mine

1. session_start();
   
2. $_SESSION['sess_var'] = "hello world!";
   
3. echo 'The content of $_SESSION[\'sess_var\'] is '
   
4.    .$_SESSION[ 'sess_var'].'<br />';
   
5. //unset($_SESSION['sess_var']);
   
6. 
   
7. session_destroy();

复制代码

出现400错误怎么回事?