[Typo3] How to send form data to Page PHP Content

[Mark Gillingham]

I'm converting a site to T3 and have some pages that access external 
MySQL data through forms. For example, in one form, I ask for a 
geographical state and content type and use this information to create 
and limit a query.

I discovered the Page PHP Content was useful to create a query and 
displaying data. I can't determine how I could feed it form entries to 
modify the SELECT statement. Is this documented somewhere that I've 
missed? Should I be doing this in another way (e.g., extension)?

The more I learn, the more confused I seem to be.

Mark