how to know IF a session is started

[sfullman]

I know functions session_start() and sessionid() - but I have a situation where I'm needing to include a page which normally does session_start(), where that may have already been done. Is there any way to do this:

if(!session_is_started())session_start();

thanks, I didn't see anything like it in the php documents.
Samuel

[NogDog]

if(session_id() == "")
{
   session_start();
}