把它放在你的 PHP 开始标签之后 ... like this

Put it after your PHP start tag <?php ... like this

<?php
session_start();
//... your code....


//more code....

阅读 PHP 手册中有关会话的更多信息.这里

Read more on sessions from the PHP Manual. Here

注意:另外请记住，如果您使用会话变量，则需要在每个页面上调用 session_start();.

Note : Also keep in mind, you need to call session_start(); on each and every page if you are making use of session variables.