how to prevent session_start() error

[nickiehow]

hi guys,
how do you prevent session_start() error. I having an notice error

A session had already been started - ignoring session_start() in D:\ProjectsWeb\test\cart.php on line 2

[rehfeld]

well, the simple answer is only call session_start() once

but if for some reason thats not easily done, you could do this

if (!session_id()) {
    session_start();
}