What does "Warning: session_start()" mean

[pjmuk]

I keep receiving this error message, could someone explain its meaning and how to rectify it

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /usr/home/gavinm/public_html/production/index.php:5) in /usr/home/gavinm/public_html/production/login/loggedin.php on line 3

Thanks in advance
Phil

[bodzan]

...make sure that you have no output to the browser before sesion_start() statement... Even a space character before <?php can mess things up in this case...

Basically when any output is sent to the browser it is sent through HTTP and thus the headers are sent as well and you cannot modify them once they are sent...

I could be wrong but I think this is basically it...

[Drakla]

It means before you call session start you can't have any output at all, not even a space before your opening php tag. If you include / require another file and that starts outputting, or has anything before their opening tags... boom! Same story. You either go cleaning up or do some output buffering, I suggest the former.