Warning: session_start(): Cannot send session cookie - headers already sent by (output started at [duplicate]

Answer 1

Move the session_start(); to top of the page always.

<?php
@ob_start();
session_start();
?>

Answer 2

You cannot session_start(); when your buffer has already been partly sent.

This mean, if your script already sent informations (something you want, or an error report) to the client, session_start() will fail.

Answer 3

1. session_start() must be at the top of your source, no html or other output befor!
2. your can only send session_start() one time
3. by this way if(session_status()!=PHP_SESSION_ACTIVE) session_start()