php blocking when calling the same file concurrently

Question

i\'m having some really strange problem.

i wrote a filemanager in PHP with the ability to download files -- which works fine. the whole script is built as one big file.<

Answer 1

Do you use sessions?

If yes, then that's probably the problem. The default session handler uses files which have to be locked while session-enabled code is executed. Practically this means that each user executes PHP files sequentially. To solve this you must use a custom session handler that uses a DB. Read this.

Edit: I want to point out that writing a custom session handler with no locking can be difficult and introduce various subtle bugs. Read more docs on this if you need to do it!

Edit 2: Sometimes using session_write_close() to close the session when no longer needed is enough (see the comments).