What permission do you have on the database for the accounts that have PHP sharing on them?
You can use a "guest" account (no login required - NOT recommended).
You can pass the login in the URL ( NOT NOT NOT recommended).
You can hard-code the login in the PHP page that is called
what are you using for the php pages? have you created them yourself? did you use the site assistant to create the php pages? are you using the FM PHP API?