I commonly use two or more "submit" buttons.
<input type='submit' name='display_button' value='Delete'>Delete
<input type='submit' name='display_button' value='Update'>Update
Normally the form post command goes back to the top of the same page where I place different functions to do the required processing
if ($display_name == "Delete") {
// do the delete processing
}
elseif (if ($display_name == "Update") {
// do the update processing
}
You do not have to direct to any other page.
Alternatively, if you have a long list of customers to select the one you want to update from, I use a link process when the customer list is first drawn from the database.
Make one variable (eg: customer name) thus
<a href='update.php?name=$name'>$name</a>
When you sellect and click on the name it goes to the next page 'update.php' which should be a form already filled in with the customer details whose name you sent across in the link above.