PHP session does not work in sub directory & kills existing session

Question

I have 3 environments for PHP.

1. Local
2. Staging
3. Live

The issue is that when I calling session in sub directory after session_start() that gives error that headers are already sent & kills existing session. And If I do not start session then it gives error for Undefined variable _SESSION.

Session is working only in ROOT directory. but not work in Subdirectory.

This only occurs on Live Environment. This same code is working on Local & Staging but not on Live.

I don't know but this may be PHP configuration issue. Please guide me.

Answer 1

Add session_start() at the beginning of your main page. Please ensure that if you are including some other file, session_start() is not defined there else error will display.