An uncaught Exception was encountered

Like the error says, you aren't passing an $id to Employee::view_profile().
If you want to remove that error message and let the function die, you can change it into the following and pass a default value.

PHP Code:

public function view_profile($id = 0)
{
   if ( !$id )
   {
       exit;
   }
   // your code here
}