检查 PHP 会话是否已经启动 [英] Check if PHP session has already started

问题描述

我有一个 PHP 文件，有时从已启动会话的页面调用，有时从未启动会话的页面调用.因此，当我在此脚本上使用 session_start() 时，有时会收到会话已启动"的错误消息.为此，我放置了以下几行:

I have a PHP file that is sometimes called from a page that has started a session and sometimes from a page that doesn't have session started. Therefore when I have session_start() on this script I sometimes get the error message for "session already started". For that I've put these lines:

if(!isset($_COOKIE["PHPSESSID"]))
{
  session_start();
}

但这次我收到了这条警告信息:

but this time I got this warning message:

注意:未定义变量:_SESSION

Notice: Undefined variable: _SESSION

有没有更好的方法来检查会话是否已经开始?

Is there a better way to check if session has already started?

如果我使用 @session_start 会使事情正常工作并关闭警告吗?

If I use @session_start will it make things work properly and just shut up the warnings?

推荐答案

PHP >= 5.4.0 , PHP 7 版本的推荐方式

if (session_status() === PHP_SESSION_NONE) {
    session_start();
}

参考:http://www.php.net/manual/en/function.session-status.php

对于 PHP < 的版本5.4.0

if(session_id() == '') {
    session_start();
}

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