function pager_default_initialize

pager_default_initialize($total, $limit, $element = 0)

Initializes a pager.

This function sets up the necessary global variables so that the render system will correctly process #type 'pager' render arrays to output pagers that correspond to the items being displayed.

If the items being displayed result from a database query performed using Drupal's database API, and if you have control over the construction of the database query, you do not need to call this function directly; instead, you can simply extend the query object with the 'PagerSelectExtender' extender before executing it. For example:

  $query = db_select('some_table')
    ->extend('Drupal\Core\Database\Query\PagerSelectExtender');

However, if you are using a different method for generating the items to be paged through, then you should call this function in preparation.

The following example shows how this function can be used in a controller that invokes an external datastore with an SQL-like syntax:

  // First find the total number of items and initialize the pager.
  $where = "status = 1";
  $total = mymodule_select("SELECT COUNT(*) FROM data " . $where)->result();
  $num_per_page = \Drupal::config('mymodule.settings')->get('num_per_page');
  $page = pager_default_initialize($total, $num_per_page);

  // Next, retrieve the items for the current page and put them into a
  // render array.
  $offset = $num_per_page * $page;
  $result = mymodule_select("SELECT * FROM data " . $where . " LIMIT %d, %d", $offset, $num_per_page)->fetchAll();
  $render = [];
  $render[] = [
    '#theme' => 'mymodule_results',
    '#result' => $result,
  ];

  // Finally, add the pager to the render array, and return.
  $render[] = ['#type' => 'pager'];
  return $render;

A second example involves a controller that invokes an external search service where the total number of matching results is provided as part of the returned set (so that we do not need a separate query in order to obtain this information). Here, we call pager_find_page() to calculate the desired offset before the search is invoked:

  // Perform the query, using the requested offset from pager_find_page().
  // This comes from a URL parameter, so here we are assuming that the URL
  // parameter corresponds to an actual page of results that will exist
  // within the set.
  $page = pager_find_page();
  $num_per_page = \Drupal::config('mymodule.settings')->get('num_per_page');
  $offset = $num_per_page * $page;
  $result = mymodule_remote_search($keywords, $offset, $num_per_page);

  // Now that we have the total number of results, initialize the pager.
  pager_default_initialize($result->total, $num_per_page);

  // Create a render array with the search results.
  $render = [];
  $render[] = [
    '#theme' => 'search_results',
    '#results' => $result->data,
    '#type' => 'remote',
  ];

  // Finally, add the pager to the render array, and return.
  $render[] = ['#type' => 'pager'];
  return $render;

Parameters

int $total: The total number of items to be paged.

int $limit: The number of items the calling code will display per page.

int $element: (optional) An integer to distinguish between multiple pagers on one page.

Return value

int The number of the current page, within the pager represented by $element. This is determined from the URL query parameter \Drupal::request()->query->get('page), or 0 by default. However, if a page that does not correspond to the actual range of the result set was requested, this function will return the closest page actually within the result set.

File

core/includes/pager.inc, line 127

Functions to aid in presenting database results as a set of pages.

Code

function pager_default_initialize($total, $limit, $element = 0) {
  global $pager_page_array, $pager_total, $pager_total_items, $pager_limits;

  $page = pager_find_page($element);

  // We calculate the total of pages as ceil(items / limit).
  $pager_total_items[$element] = $total;
  $pager_total[$element] = ceil($pager_total_items[$element] / $limit);
  $pager_page_array[$element] = max(0, min($page, ((int) $pager_total[$element]) - 1));
  $pager_limits[$element] = $limit;
  return $pager_page_array[$element];
}