Here's the situation; below is a piece of PHP code which is frequently reused.
if (! isset($_REQUEST['process_form'])
{
   // render form
   echo "<form>";
   // snipped
   // important bit! Remember which id we are processing
   echo "<input hidden='id' value='$id'>";
   // snipped
} else {
  // process the form
}
I wish to encapsulate this into a function, akin to
  class ProcessForm() {
   function execute(array $request, $id) { };
  }
The issue here is; the $id parameter is only needed when rendering the form. When processing the form after a user input or through an AJAX handler, I don't need the $id at all.
How could I refactor to get rid of the optional variable $id?
 
    