reactivating a query after executing an insert statement in PHP/MYSQL

reactivating a query after executing an insert statement in PHP/MYSQL

I have 2 forms. The first form the user would select a department (DEPQ)
from a drop down menu list. Once that is done they would submit that form
and the results would be displayed in a drop down menu in the second form.
The user would then use this second form to insert data into a table in
msql database using the derived values. What I am trying to do is once the
system has completed the insertion of the data, the system automatically
re populates the drop down menu with the results derived from first query.
I know this can be simply achieved with multiple linked drop down menu's
but I have been unable to find a suitable tutorial for this function. Any
help you all can give me would be greatly appreciated.