Why is __wakeup() called on my object when I session_start()?

Question

I have a following problem:

I use a class with singleton pattern, i made the __wakeup() private for that reason. At no point is that object being stored in session. When i call session_start(), i get this error message:

Warning: Invalid callback MySingletonClass::__wakeup, cannot access private method MySingletonClass::__wakeup() in Session.php on line 32

line 32 of Session.php reads:

30 public function startSession() {
31     if (session_status() == PHP_SESSION_NONE) {
32         session_start();
33     }
34 }

I understand that objects stored in session are being serialized and unserialized, but MySingletonClass is never stored in session... In fact, the $_SESSION array is empty.

I was thinking that maybe i stored it in session by accident sometime and it sits there, but this persists even if i clear all $_SESSION data, destroy the session, delete session files on server, restart Apache and start new session...

What's even weirder is that i use several different classes that use exact same singleton pattern, have private __wakeup(), and they never raise this problem. Its just this one.

What is going on? Is my code so insane php got confused?

[edit] I figured something out:

This error happens if session_start() is called AFTER the MySingletonClass has been defined (so after the file containing its definition has been included/required) but does not if session_start() is moved to the very beginning of script execution, before any other files are included/required.

Does anyone have an explanation here? Having session_start() earlier is fine I guess, I would start it anyhow, but I would like to know what is happening here...

Answer 1

I resolved the issue - the problem was in my autoloading procedure. I think. Perhaps.

To be honest, i have no clue what was really wrong, but after i scrapped my autoloader class, and re-wrote it from scratch, the error message disappeared so i assume it was autoloader that was at fault.

Your guess is as good as mine.

Answer 2

Just had the same problem, with PHPUnit 5.7.27.

In my case, backupGlobals was set to "true". Setting it to false, in my phpunit.xml, fixed it.