How to insert data from db and retrieve id for particular item from combobox ? can anyone help me?

Question

I've one table for supplier name (combobox 1)and 2nd table Medicine name(combobox 2)
And the third table for form which i have to insert data from combobox 1&2 into 3rd table.

Answer 1

Php+mysql:
Select table1.supplierName, table2.MedicineName From table1,table2
Where ...
Fetch in variables in php
Insert into table3 (columnName1,..) Values (fetchesValue)