Creating a field that will give an array when submitted

Form element

  <input type="checkbox" name="UserIsActive[$UserId]" value="YES" />
  <input type="text" name="UserName[$UserId]" value="" />

Form handler

  if (isset($_POST['UserName']))
  {
    foreach ($_POST['UserName'] as $UserId => $UserName)    //Will always be present
    {
      $IsActive = isset($_POST['UserIsActive'][$UserId]);    //Checkboxes will only be present when checked

      //$UserId
      //$UserName
      //$IsActive (true/false)
    }
  }