php 检查会话是否设置，如果没有，创建一个？
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Check if session is set or not, and if not create one?
提问by Fireworksable
I want to check if a session is currently set, and if so do allow the page to run as normal (do nothing) if not create a session.
我想检查当前是否设置了会话，如果是这样，如果不创建会话，则允许页面正常运行（什么都不做）。
I had a look at another SO question, in which the following code was posted:
我查看了另一个 SO 问题，其中发布了以下代码：
if ( empty( $_SESSION['login'] )) { } else { }
Would the easiest way to do this be to set something like $_SESSION['a']for each session, and then run if(empty($_SESSION['a']))to check if a session exists?
最简单的方法是$_SESSION['a']为每个会话设置类似的东西，然后运行if(empty($_SESSION['a']))以检查会话是否存在？
Then again, can you use a session variable without invoking session_start() in the first place, thus making it obsolete (I tried this yesterday, as an echo though, not an if statement to check that a variable was carrying through without realizing that session_start() needed to be invoked before I could echo the variable).
再说一次，你能不能在不调用 session_start() 的情况下使用 session 变量，从而使它过时（我昨天试过这个，作为回声，而不是 if 语句来检查变量是否正在执行而没有意识到 session_start () 需要在我可以回显变量之前调用）。
There's probably an easy way that's oft used, I just can't seem to find it.
可能有一种经常使用的简单方法，我似乎找不到它。
Any help would be greatly appreciated!
任何帮助将不胜感激！
回答by Chris Hepner
session_id()returns the string identifying the current session. If a session hasn't been initialized, it will return an empty string.
session_id()返回标识当前会话的字符串。如果会话尚未初始化，它将返回一个空字符串。
if(session_id())
{
// session has been started
}
else
{
// session has NOT been started
session_start();
}
