I'll give you some input on this when I get into the office... it's not vey complex!
Mike.
*** EDIT
I was going to try and explain it to you myself, but I found I too had to keep referring to the following pages to make sure my instructions were correct, so in the end, I figured it will probably be more helpful to you to have these resources at hand:
kirupa.com - Flash Based Email Form Using PHP
^^This one is good for explaining forms and database interaction
codewalkers.com - php tutorials - Creating a Mail Form with PHP and Flash - PHP Help
^^ This one is a little more indepth
codewalkers.com - php tutorials - Creating a Mail Form with PHP and Flash - Part 2 - PHP Help
^^ This is part two... a little more complex form handling
Adobe - Developer Center : Business Directory Sample: Flash MX 2004 Professional with PHP and MySQL
Macromedia - Developer Center : Connecting Macromedia Flash and PHP
Macromedia - Developer Center : Macromedia Flash MX and PHP
^^ These are the official words on the subject... I found these to be the most useful
Dynamic Flash database with PHP, ASP, CFM remoting and web services community
^^ Of couse, like every subject, there is a page dedicated to this issue
I hope this helps... and if you find you have specific questions not answered in these pages, feel free to drop me a not and I will help if I can.
Mike.