Pagination

When there are too much data to be displayed on a single page, a common strategy is to display them in multiple pages and on each page only display a small portion of the data. This strategy is known as pagination.

Yii uses a yii\data\Pagination object to represent the information about a pagination scheme. In particular,

• total count specifies the total number of data items. Note that this is usually much more than the number of data items needed to display on a single page.
• page size specifies how many data items each page contains. The default value is 20.
• current page gives the current page number (zero-based). The default value is 0, meaning the first page.

With a fully specified yii\data\Pagination object, you can retrieve and display data partially. For example, if you are fetching data from a database, you can specify the OFFSET and LIMIT clause of the DB query with the corresponding values provided by the pagination. Below is an example,

use yii\data\Pagination;

// build a DB query to get all articles with status = 1
$query = Article::find()->where(['status' => 1]);

// get the total number of articles (but do not fetch the article data yet)
$count = $query->count();

// create a pagination object with the total count
$pagination = new Pagination(['totalCount' => $count]);

// limit the query using the pagination and retrieve the articles
$articles = $query->offset($pagination->offset)
    ->limit($pagination->limit)
    ->all();

Which page of articles will be returned in the above example? It depends on whether a query parameter named page is given. By default, the pagination will attempt to set the current page to be the value of the page parameter. If the parameter is not provided, then it will default to 0.

To facilitate building the UI element that supports pagination, Yii provides the yii\widgets\LinkPager widget that displays a list of page buttons upon which users can click to indicate which page of data should be displayed. The widget takes a pagination object so that it knows what is the current page and how many page buttons should be displayed. For example,

use yii\widgets\LinkPager;

echo LinkPager::widget([
    'pagination' => $pagination,
]);

If you want to build UI element manually, you may use yii\data\Pagination::createUrl() to create URLs that would lead to different pages. The method requires a page parameter and will create a properly formatted URL containing the page parameter. For example,

// specifies the route that the URL to be created should use
// If you do not specify this, the currently requested route will be used
$pagination->route = 'article/index';

// displays: /index.php?r=article%2Findex&page=100
echo $pagination->createUrl(100);

// displays: /index.php?r=article%2Findex&page=101
echo $pagination->createUrl(101);

Tip: You can customize the name of the page query parameter by configuring the pageParam property when creating the pagination object.