How to Create a Drupal Views Items Per Page Filter

Sometimes, depending on the site you are working on, you need to allow (or the client wants you to allow ;)) visitors to be able to select how many items per page will be displayed e.g. on a product listings page.

To do this in Drupal 6 turned out to be a lot easier than I thought. I used the code from this blog post by Nicholas Coates but, rather than add it to a views template, I added it to a hook_views_query_alter function I was already using. This meant I could easily use the $view object passed as a parameter to this function:

function hook_views_query_alter(&$view, &$query) {
  ...
  $itemCount = $_GET['itemcount']; // this is just as an example
  if ($itemCount == 0) {
    $view->set_items_per_page(10);
  } else {
    $view->set_items_per_page($itemCount);
  }
	...
}

As Nicholas Coates says in his aforementioned blog post: this is a quick and painless way to implement an items per page filter.