我有一个由 HTML (AngularJS) 客户端和 PHP 后端组成的应用程序。客户端和服务器之间的所有通信都是使用 XMLHTTPRequests 完成的（当然除了加载第一个 HTML 文件和静态资源 - JS/CSS ...）。服务器公开一些 API 端点，客户端向这些 URL 发出请求。一旦服务器收到请求，它会检查 $_SESSION 以检查用户是否已登录。
我的问题是，是否有可能在几乎每个请求时从 $_SESSION 读取（而不是写入）可能会导致响应严重挂起？例如，应用程序处理多个请求，然后发送随机请求并在几分钟后收到响应（到目前为止记录了 15 个）。似乎请求处理得太晚了（根据 dummy error_log 测试），所以减速不是由 PHP 我的代码中的操作引起的。
也许这是一个愚蠢的问题，但我已经将 apache 的 ServerLimit (1000) 翻了一番，但没有运气。我在这台服务器上还有另一个 PHP 应用程序工作正常，我能想到的唯一区别是工作应用程序几乎没有检查 $_SESSION 与 XMLHTTPRequests 的组合。
PHP版本：5.3.3
I could not find a specific reason for your problem but there if you are using php 5.1.x it loads all session data in to memory at session_start() . As a result of this file access in the entire server will be delayed .
If your server php version is not 5.1 and if it is latest 5.4 or .5 then , the possible problem would come due to creation of large number of session temp files .
This some times causes problems with filesystem limits in operating system . so you need to set the session time out to less period .
Also while reading there will be much load on the operating system .
This can be achieved by using config parameter session.gc_maxlifetime
PHP runs garbage collection on expired sessions after the current session is loaded and by using session.gc_probability and session.gc_divisor it calculates the probability that garbage collection will run.
So set session maxlife time to max 1 and see the performance .
Because of this reason most of the web applications provide an option called remember me.
And those applications usually replaces session_start and enforces a timeout if user is idle for a particular span of time .
Hope this helps
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