session_is_started()

Hello,

I'm makeing a PHP frontend to a postgresql db, and want to use
sessions in order to sore global variables. I read that it's enough to
put session_start() in the top file of the app, but that doesn't work,
when I go two or three PHP files "deep", the session is forgotten.

To workaround this, I tried putting session_start() at the begonning
of every PHP file that does something with session variables. This
however gives me lot of these errors: "Notice: A session had already
been started - ignoring session_start() in [scriptname] on line 5"

I would like something like

if (!session_is_started()) { // note: this function doesn't exist
  session_start();
}

How have you solved this problem? Thanks for any tips!

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15:36-15:40
Fedora Core release 1 (Yarrow) Linux 2.4.22-1.2174.nptl