An old PHP bug: Duplicate Set-Cookie header received?
#How to solve the problem when PHP outputs duplicate Session Set-Cookie headers?
I encountered an old bug today that I had never discovered before. The front-end response received two duplicate Set-Cookie headers.
I was puzzled and after a long time of troubleshooting, I finally determined that it was caused by repeated calls to the session_start() function.
Every time the session_start() function is called, a Set-Cookie header will be output.
Solution:
session_start(); session_abort(); header_remove('Set-Cookie'); // 移除 Set-Cookie 头
Expansion:
The corresponding session file is locked after session_start() and will not be unlocked until the end of the current script .
During the lock period, if a process accesses the same session id, session_start() will not start until the file is unlocked.
session_start(); //starts the session,独占对应session id的文件 $_SESSION['user']="Me"; 将变量写入对应的session 文件 session_write_close(); // close write capability ,关闭对文件 的 写独占 echo $_SESSION['user']; // you can still access it ,依然可以对文件进行 写操作
session.cookie_lifetime defaults to 0, which means that the cookie becomes invalid when the browser is closed.
In addition to configuring cookie_lifetime in php.ini, it can also be set through the function session_set_cookie_params.
session.gc_maxlifetime The default is 1440 seconds, that is to say, if the time interval between two user requests exceeds 1440 seconds,
The server-side session file will be treated as garbage by PHP, if gc_probability/gc_divisor equals 1 , the session file will be deleted and recycled.
Set the session cookie and session file to expire after 86400 seconds (1 day):
session.cookie_lifetime=86400 session.gc_maxlifetime=86400 session.gc_probability=1 session.gc_divisor=1
Recommended learning: "PHP Video Tutorial 》
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