php - 对 $_SESSION 的每次访问都立即涉及文件系统的 i/o 吗？

Question

每次我访问 $_SESSION 中的数据时，它是立即更新磁盘上的 session 文件，还是仅在进程停止时更新一次？或者每n个字节的数据变化(刷新)？

这个问题不一定是关于具体的文件 session 处理程序，而是每一个处理程序。 (除了在内存中存储普通变量之外， session 中的每次触摸都会立即调用任何类型的 I/O)。

Answer 1

正如 Matt 所写，它默认在脚本执行结束时写入。您可以在此处阅读 session_write_close()

Session data is usually stored after your script terminated without the need to call session_write_close(), but as session data is locked to prevent concurrent writes only one script may operate on a session at any time. When using framesets together with sessions you will experience the frames loading one by one due to this locking. You can reduce the time needed to load all the frames by ending the session as soon as all changes to session variables are done.