Dynamic SQL in PHP

i'm currently coding a plugin in PHP and i have a listbox containing numbers from 1 to 30 and a "submit" button. The plugin page is running some SQL request.

The point is the SQL request should update when you choose a number in the listbox and click the submit button. For instance :

SELECT G.xxx FROM yyy M, zzz G WHERE M.name = G.nomfield AND G.nomfield = "xxx" AND G.idfield = 01 AND G.xxx = $numberfrom1to30

the display should be different according to the number selected in the listbox after the submit button is clicked. How should i do this ?

Thanks alot