dynamic selection of database

hey frnds...

i am develpoing a program using PHP/MySQL. Here, i have a form which consists of a few text fields etc etc. It also contains a drop down menu.

In the backend, i have a number of databases. The user input (drop down menu) will decide which database is connected to.

Please help me with the code for the same. I want to strict to PHP/TML only, and not use javascript.

pls help.

thx..