In PHP, is there any harm in running session_start() multiple times?

Question

Presumably there\'s some tiny performance hit, but beyond that?

Answer 1

Reading the docs for session_start, all I can see is:

As of PHP 4.3.3, calling session_start() after the session was previously started will result in an error of level E_NOTICE. Also, the second session start will simply be ignored.

So, you'll get an E_NOTICE and be ignored.