redirect to child on save passing masterkey1

I have two tables
tbl_time

tbl_expense
The employees enter how much time they worked in tbl_time. Then, they can enter any expenses and upload receipts in the child table (tbl_expense)
I would like it so when you add a time entry and hit save it takes you to the tbl_expense add page using the id from the time entry you just saved.
So, how would I change the code on event so the ##### below are populated with the id from tbl_time record that was just saved (parent).
//** Redirect to another page ****

header("Location: tbl_expense_add.php?mastertable=tbl_time&masterkey1=#######);

exit();