Submitting form to PHP

You’re trying to combine isset with a value comparison, and that’s not how it works. You should rewrite this:

if(isset($_POST['Client_Type_Edit']) == 'Individual')

to this:

if ( isset( $_POST['Client_Type_Edit'] ) && 'Individual' === $_POST['Client_Type_Edit'] )

This is checking to make sure that $_POST['Client_Type_Edit'] is set AND the value is equal to “Individual”.

Now repeat that for all of them.