php - PHP 如何知道何时删除 session ？

Question

我认为 session 存储在客户端，因为 session 在浏览器关闭时被删除。然而，今天有人告诉我这不是真的， session 存储在服务器上。

那么 session 如何知道浏览器何时关闭，以便 session 被删除？

Answer 1

事实并非如此。有两个因素在起作用:

• lifetime of the cookie在客户端；此 cookie 包含 session ID。它与 session 数据本身没有任何关系。

  The manual probably doesn't stress this enough:

  This has nothing to do with lifetime of a session

  Whatever you set this setting to, it won't change how long sessions live on your server.

  This only changes HTTP cache expiration time (Expires: and Cache-Control: max-age headers), which advise browser for how long it can keep pages cached in user's cache without having to reload them from the server.

• 服务器端 session 数据的生命周期；通过使用来自客户端的 session ID 进行查找来“激活” session 。它的生命周期通过 session garbage collection settings discussed here 控制.

  一位评论者在 session.cache_expire 文档页面上发帖，大概是在谈论 session 数据:

  What most people also don't know, is that most Linux distributions (Debian and Ubuntu for me atleast) have a cronbjob that cleans up your session dir using the value set in the global /etc/php5/php.ini (which defaults to 24mins). So even if you set a value larger in your scripts, the cronbjob will still cleanup sessions using the global value.

  If you run into that situation, you can set the global value higher in /etc/php5/php.ini, disable the cronjob or even better, do your own session cleanup in a non-systemwide directory or a database.

  如您所见，在区分 session 跟踪和 session 数据存储时，社区中存在很多混淆。