5 * Functions to aid in presenting database results as a set of pages.
8 use Drupal\Component\Utility\UrlHelper;
11 * Returns the current page being requested for display within a pager.
14 * (optional) An integer to distinguish between multiple pagers on one page.
17 * The number of the current requested page, within the pager represented by
18 * $element. This is determined from the URL query parameter
19 * \Drupal::request()->query->get('page'), or 0 by default. Note that this
20 * number may differ from the actual page being displayed. For example, if a
21 * search for "example text" brings up three pages of results, but a user
22 * visits search/node/example+text?page=10, this function will return 10,
23 * even though the default pager implementation adjusts for this and still
24 * displays the third page of search results at that URL.
26 * @see pager_default_initialize()
28 function pager_find_page($element = 0) {
29 $page = \Drupal::request()->query->get('page', '');
30 $page_array = explode(',', $page);
31 if (!isset($page_array[$element])) {
32 $page_array[$element] = 0;
34 return (int) $page_array[$element];
38 * Initializes a pager.
40 * This function sets up the necessary global variables so that the render
41 * system will correctly process #type 'pager' render arrays to output pagers
42 * that correspond to the items being displayed.
44 * If the items being displayed result from a database query performed using
45 * Drupal's database API, and if you have control over the construction of the
46 * database query, you do not need to call this function directly; instead, you
47 * can simply extend the query object with the 'PagerSelectExtender' extender
48 * before executing it. For example:
50 * $query = db_select('some_table')
51 * ->extend('Drupal\Core\Database\Query\PagerSelectExtender');
54 * However, if you are using a different method for generating the items to be
55 * paged through, then you should call this function in preparation.
57 * The following example shows how this function can be used in a controller
58 * that invokes an external datastore with an SQL-like syntax:
60 * // First find the total number of items and initialize the pager.
61 * $where = "status = 1";
62 * $total = mymodule_select("SELECT COUNT(*) FROM data " . $where)->result();
63 * $num_per_page = \Drupal::config('mymodule.settings')->get('num_per_page');
64 * $page = pager_default_initialize($total, $num_per_page);
66 * // Next, retrieve the items for the current page and put them into a
68 * $offset = $num_per_page * $page;
69 * $result = mymodule_select("SELECT * FROM data " . $where . " LIMIT %d, %d", $offset, $num_per_page)->fetchAll();
72 * '#theme' => 'mymodule_results',
73 * '#result' => $result,
76 * // Finally, add the pager to the render array, and return.
77 * $render[] = ['#type' => 'pager'];
81 * A second example involves a controller that invokes an external search
82 * service where the total number of matching results is provided as part of
83 * the returned set (so that we do not need a separate query in order to obtain
84 * this information). Here, we call pager_find_page() to calculate the desired
85 * offset before the search is invoked:
87 * // Perform the query, using the requested offset from pager_find_page().
88 * // This comes from a URL parameter, so here we are assuming that the URL
89 * // parameter corresponds to an actual page of results that will exist
91 * $page = pager_find_page();
92 * $num_per_page = \Drupal::config('mymodule.settings')->get('num_per_page');
93 * $offset = $num_per_page * $page;
94 * $result = mymodule_remote_search($keywords, $offset, $num_per_page);
96 * // Now that we have the total number of results, initialize the pager.
97 * pager_default_initialize($result->total, $num_per_page);
99 * // Create a render array with the search results.
102 * '#theme' => 'search_results',
103 * '#results' => $result->data,
104 * '#type' => 'remote',
107 * // Finally, add the pager to the render array, and return.
108 * $render[] = ['#type' => 'pager'];
113 * The total number of items to be paged.
115 * The number of items the calling code will display per page.
116 * @param int $element
117 * (optional) An integer to distinguish between multiple pagers on one page.
120 * The number of the current page, within the pager represented by $element.
121 * This is determined from the URL query parameter
122 * \Drupal::request()->query->get('page), or 0 by default. However, if a page
123 * that does not correspond to the actual range of the result set was
124 * requested, this function will return the closest page actually within the
127 function pager_default_initialize($total, $limit, $element = 0) {
128 global $pager_page_array, $pager_total, $pager_total_items, $pager_limits;
130 $page = pager_find_page($element);
132 // We calculate the total of pages as ceil(items / limit).
133 $pager_total_items[$element] = $total;
134 $pager_total[$element] = ceil($pager_total_items[$element] / $limit);
135 $pager_page_array[$element] = max(0, min($page, ((int) $pager_total[$element]) - 1));
136 $pager_limits[$element] = $limit;
137 return $pager_page_array[$element];
141 * Compose a URL query parameter array for pager links.
144 * A URL query parameter array that consists of all components of the current
145 * page request except for those pertaining to paging.
147 function pager_get_query_parameters() {
148 $query = &drupal_static(__FUNCTION__);
149 if (!isset($query)) {
150 $query = UrlHelper::filterQueryParameters(\Drupal::request()->query->all(), ['page']);
156 * Prepares variables for pager templates.
158 * Default template: pager.html.twig.
160 * Menu callbacks that display paged query results should use #type => pager
161 * to retrieve a pager control so that users can view other results. Format a
162 * list of nearby pages with additional query results.
164 * @param array $variables
165 * An associative array containing:
166 * - pager: A render element containing:
167 * - #tags: An array of labels for the controls in the pager.
168 * - #element: An optional integer to distinguish between multiple pagers on
170 * - #parameters: An associative array of query string parameters to append
171 * to the pager links.
172 * - #route_parameters: An associative array of the route parameters.
173 * - #quantity: The number of pages in the list.
175 function template_preprocess_pager(&$variables) {
176 $element = $variables['pager']['#element'];
177 $parameters = $variables['pager']['#parameters'];
178 $quantity = $variables['pager']['#quantity'];
179 $route_name = $variables['pager']['#route_name'];
180 $route_parameters = isset($variables['pager']['#route_parameters']) ? $variables['pager']['#route_parameters'] : [];
181 global $pager_page_array, $pager_total;
183 // Nothing to do if there is only one page.
184 if ($pager_total[$element] <= 1) {
188 $tags = $variables['pager']['#tags'];
190 // Calculate various markers within this pager piece:
191 // Middle is used to "center" pages around the current page.
192 $pager_middle = ceil($quantity / 2);
193 // current is the page we are currently paged to.
194 $pager_current = $pager_page_array[$element] + 1;
195 // first is the first page listed by this pager piece (re quantity).
196 $pager_first = $pager_current - $pager_middle + 1;
197 // last is the last page listed by this pager piece (re quantity).
198 $pager_last = $pager_current + $quantity - $pager_middle;
199 // max is the maximum page number.
200 $pager_max = $pager_total[$element];
201 // End of marker calculations.
203 // Prepare for generation loop.
205 if ($pager_last > $pager_max) {
206 // Adjust "center" if at end of query.
207 $i = $i + ($pager_max - $pager_last);
208 $pager_last = $pager_max;
211 // Adjust "center" if at start of query.
212 $pager_last = $pager_last + (1 - $i);
215 // End of generation loop preparation.
217 // Create the "first" and "previous" links if we are not on the first page.
218 if ($pager_page_array[$element] > 0) {
219 $items['first'] = [];
221 'query' => pager_query_add_page($parameters, $element, 0),
223 $items['first']['href'] = \Drupal::url($route_name, $route_parameters, $options);
224 if (isset($tags[0])) {
225 $items['first']['text'] = $tags[0];
228 $items['previous'] = [];
230 'query' => pager_query_add_page($parameters, $element, $pager_page_array[$element] - 1),
232 $items['previous']['href'] = \Drupal::url($route_name, $route_parameters, $options);
233 if (isset($tags[1])) {
234 $items['previous']['text'] = $tags[1];
238 if ($i != $pager_max) {
239 // Add an ellipsis if there are further previous pages.
241 $variables['ellipses']['previous'] = TRUE;
243 // Now generate the actual pager piece.
244 for (; $i <= $pager_last && $i <= $pager_max; $i++) {
246 'query' => pager_query_add_page($parameters, $element, $i - 1),
248 $items['pages'][$i]['href'] = \Drupal::url($route_name, $route_parameters, $options);
249 if ($i == $pager_current) {
250 $variables['current'] = $i;
253 // Add an ellipsis if there are further next pages.
254 if ($i < $pager_max + 1) {
255 $variables['ellipses']['next'] = TRUE;
259 // Create the "next" and "last" links if we are not on the last page.
260 if ($pager_page_array[$element] < ($pager_max - 1)) {
263 'query' => pager_query_add_page($parameters, $element, $pager_page_array[$element] + 1),
265 $items['next']['href'] = \Drupal::url($route_name, $route_parameters, $options);
266 if (isset($tags[3])) {
267 $items['next']['text'] = $tags[3];
272 'query' => pager_query_add_page($parameters, $element, $pager_max - 1),
274 $items['last']['href'] = \Drupal::url($route_name, $route_parameters, $options);
275 if (isset($tags[4])) {
276 $items['last']['text'] = $tags[4];
280 $variables['items'] = $items;
282 // The rendered link needs to play well with any other query parameter used
283 // on the page, like exposed filters, so for the cacheability all query
284 // parameters matter.
285 $variables['#cache']['contexts'][] = 'url.query_args';
289 * Gets the URL query parameter array of a pager link.
291 * Adds to or adjusts the 'page' URL query parameter so that if you follow the
292 * link, you'll get page $index for pager $element on the page.
294 * The 'page' URL query parameter is a comma-delimited string, where each value
295 * is the target content page for the corresponding pager $element. For
296 * instance, if we have 5 pagers on a single page, and we want to have a link
297 * to a page that should display the 6th content page for the 3rd pager, and
298 * the 1st content page for all the other pagers, then the URL query will look
299 * like this: ?page=0,0,5,0,0 (page numbering starts at zero).
301 * @param array $query
302 * An associative array of URL query parameters to add to.
303 * @param int $element
304 * An integer to distinguish between multiple pagers on one page.
306 * The index of the target page, for the given element, in the pager array.
309 * The altered $query parameter array.
311 function pager_query_add_page(array $query, $element, $index) {
312 global $pager_page_array;
314 // Build the 'page' query parameter. This is built based on the current
315 // page of each pager element (or NULL if the pager is not set), with the
316 // exception of the requested page index for the current element.
317 $max_element = max(array_keys($pager_page_array));
319 for ($i = 0; $i <= $max_element; $i++) {
320 $element_pages[] = ($i == $element) ? $index : (isset($pager_page_array[$i]) ? $pager_page_array[$i] : NULL);
322 $query['page'] = implode(',', $element_pages);
324 // Merge the query parameters passed to this function with the parameters
325 // from the current request. In case of collision, the parameters passed into
326 // this function take precedence.
327 if ($current_request_query = pager_get_query_parameters()) {
328 $query = array_merge($current_request_query, $query);