Your update server behavior is filtering the clnt_no with the value: $_GET['clnt_no']
However your form doesn't pass the clnt_no value forward in the action. The solution is probably to remove the form action attribute from the form and then it will pass the url parameters with the form submit automatically... or better yet use: $_SESSION[cclnt_no] so that the end user can't change it in the url and update a different account.