.. _zend.paginator.usage:

Usage
=====

.. _zend.paginator.usage.paginating:

Paginating data collections
---------------------------

In order to paginate items into pages, ``Zend\Paginator`` must have a generic way of accessing that data. For that
reason, all data access takes place through data source adapters. Several adapters ship with Zend Framework by
default:

.. _zend.paginator.usage.paginating.adapters:

.. table:: Adapters for Zend\\Paginator

   +-------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
   |Adapter      |Description                                                                                                                                                                          |
   +=============+=====================================================================================================================================================================================+
   |Array        |Accepts a PHP array                                                                                                                                                                  |
   +-------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
   |DbSelect     |Accepts a Zend\\Db\\Sql\\Select plus either a Zend\\Db\\Adapter\\Adapter or Zend\\Db\\Sql\\Sql to paginate rows from a database                                                      |
   +-------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
   |Iterator     |Accepts an Iterator instance                                                                                                                                                         |
   +-------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
   |Null         |Does not use Zend\\Paginator to manage data pagination. You can still take advantage of the pagination control feature.                                                              |
   +-------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

.. note::

   Instead of selecting every matching row of a given query, the DbSelect adapter retrieves only
   the smallest amount of data necessary for displaying the current page.  Because of this, a second query is dynamically generated to determine the total number of matching rows.

To create an instance of ``Zend\Paginator``, you must supply an adapter to the constructor:

.. code-block:: php
   :linenos:

   $paginator = new Zend\Paginator(new Zend\Paginator\Adapter\Array($array));

   In the case of the ``Null`` adapter, in lieu of a data collection you must supply an item count to its
   constructor.

Although the instance is technically usable in this state, in your controller action you'll need to tell the
paginator what page number the user requested. This allows advancing through the paginated data.

.. code-block:: php
   :linenos:

   $paginator->setCurrentPageNumber($page);

The simplest way to keep track of this value is through a *URL* parameter.  The following is an example route you might use in an *Array* configuration file:

.. code-block:: php
   :linenos:

   return array(
       'routes' => array(
           'paginator' => array(
               'type' => 'segment',
               'options' => array(
                   'route' => '/list/[page/:page]',
                   'defaults' => array(
                       'page' => 1,
                   ),
               ),
           ),
       ),
   );

With the above route (and using Zend Framework *MVC* components), you might set the current page number in your controller action like so:

.. code-block:: php
   :linenos:

   $paginator->setCurrentPageNumber($this->params()->fromRoute('page'));

There are other options available; see :ref:`Configuration <zend.paginator.configuration>` for more on them.

Finally, you'll need to assign the paginator instance to your view. If you're using Zend Framework *MVC* component, you can assign the paginator object to your view model:

.. code-block:: php
   :linenos:

   $vm = new ViewModel();
   $vm->setVariable('paginator', $paginator);
   return $vm;

.. _zend.paginator.usage.dbselect:

The DbSelect adapter
--------------------------------------

The usage of most adapters is pretty straight-forward. However, the database adapter requires a more detailed
explanation regarding the retrieval and count of the data from the database.

To use the DbSelect adapter you don't have to retrieve the data upfront from the database. The adapter will do the 
retrieval for you, as well as the counting of the total pages. If additional work has to be done on the database results 
which cannot be expressed via the provided ``Zend\Db\Sql\Select`` object you must extend the adapter and override the 
``getItems()`` method.

Additionally this adapter does **not** fetch all records from the database in order to count them. Instead, the
adapter manipulates the original query to produce a corresponding COUNT query. Paginator then executes that
COUNT query to get the number of rows. This does require an extra round-trip to the database, but this is many
times faster than fetching an entire result set and using ``count()``, especially with large collections of data.

The database adapter will try and build the most efficient query that will execute on pretty much any modern
database. However, depending on your database or even your own schema setup, there might be more efficient ways to
get a rowcount. For this scenario, you can extend the provided DbSelect adapter and implement a custom ``getRowCount``
method.  For example, if you keep track of the count of blog posts in a separate table, you could achieve a faster count query with the
following setup:

.. code-block:: php
   :linenos:

   class MyDbSelect extends Zend\Paginator\Adapter\DbSelect
   {
       public function count()
       {
           $sql = new Zend\Db\Sql\Select();
           $sql->from('item_counts')->columns(array('c'=>'post_count'));

           $statement = $this->sql->prepareStatementForSqlObject($select);
           $result    = $statement->execute();
           $row       = $result->current();
           $this->rowCount = $row['c'];

           return $this->rowCount;
       }
   }

   $adapter = new MyDbSelect($query, $adapter);
   $paginator = new Zend\Paginator\Paginator($adapter);

This approach will probably not give you a huge performance gain on small collections and/or simple select queries.
However, with complex queries and large collections, a similar approach could give you a significant performance
boost.

The DbSelect adapter also supports returning of fetched records using the ``Zend\Db\ResultSet`` component of ``Zend\Db``.  
You can override the concrete RowSet implementation by passing an object implementing ``Zend\Db\ResultSet\ResultSetInterface`` 
as the third constructor argument to the DbSelect adapter:

.. code-block:: php
   :linenos:

   // $objectPrototype is an instance of our custom entity
   // $hydrator is a custom hydrator for our entity (implementing Zend\Stdlib\Hydrator\HydratorInterface)
   $resultSet = new Zend\Db\ResultSet\HydratingResultSet($hydrator, $objectPrototype); 

   $adapter = new Zend\Paginator\Adapter\DbSelect($query, $dbAdapter, $resultSet)
   $paginator = new Zend\Paginator\Paginator($adapter);

Now when we iterate over ``$paginator`` we will get instances of our custom entity instead of key-value-pair arrays.

.. _zend.paginator.rendering:

Rendering pages with view scripts
---------------------------------

The view script is used to render the page items (if you're using ``Zend\Paginator`` to do so) and display the
pagination control.

Because ``Zend\Paginator`` implements the *SPL* interface `IteratorAggregate`_, looping over your items and
displaying them is simple.

.. code-block:: php
   :linenos:

   <html>
   <body>
   <h1>Example</h1>
   <?php if (count($this->paginator)): ?>
   <ul>
   <?php foreach ($this->paginator as $item): ?>
     <li><?php echo $item; ?></li>
   <?php endforeach; ?>
   </ul>
   <?php endif; ?>

   <?php echo $this->paginationControl($this->paginator,
                                       'Sliding',
                                       'my_pagination_control'); ?>
   </body>
   </html>

Notice the view helper call near the end. PaginationControl accepts up to four parameters: the paginator instance,
a scrolling style, a view script name, and an array of additional parameters.

The second and third parameters are very important. Whereas the view script name is used to determine how the
pagination control should **look**, the scrolling style is used to control how it should **behave**. Say the view
script is in the style of a search pagination control, like the one below:

.. image:: ../images/zend.paginator.usage.rendering.control.png
   :align: center

What happens when the user clicks the "next" link a few times? Well, any number of things could happen. The current
page number could stay in the middle as you click through (as it does on Yahoo!), or it could advance to the end of
the page range and then appear again on the left when the user clicks "next" one more time. The page numbers might
even expand and contract as the user advances (or "scrolls") through them (as they do on Google).

There are four scrolling styles packaged with Zend Framework:

.. _zend.paginator.usage.rendering.scrolling-styles:

.. table:: Scrolling styles for Zend\\Paginator

   +---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
   |Scrolling style|Description                                                                                                                                                          |
   +===============+=====================================================================================================================================================================+
   |All            |Returns every page. This is useful for dropdown menu pagination controls with relatively few pages. In these cases, you want all pages available to the user at once.|
   +---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
   |Elastic        |A Google-like scrolling style that expands and contracts as a user scrolls through the pages.                                                                        |
   +---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
   |Jumping        |As users scroll through, the page number advances to the end of a given range, then starts again at the beginning of the new range.                                  |
   +---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+
   |Sliding        |A Yahoo!-like scrolling style that positions the current page number in the center of the page range, or as close as possible. This is the default style.            |
   +---------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+

The fourth and final parameter is reserved for an optional associative array of additional variables that you want
available in your view (available via ``$this``). For instance, these values could include extra *URL*
parameters for pagination links.

By setting the default view script name, default scrolling style, and view instance, you can eliminate the calls to
PaginationControl completely:

.. code-block:: php
   :linenos:

   Zend\Paginator\Paginator::setDefaultScrollingStyle('Sliding');
   Zend\View\Helper\PaginationControl::setDefaultViewPartial(
       'my_pagination_control'
   );

When all of these values are set, you can render the pagination control inside your view script with a simple echo
statement:

.. code-block:: php
   :linenos:

   <?php echo $this->paginator; ?>

.. note::

   Of course, it's possible to use ``Zend\Paginator`` with other template engines. For example, with Smarty you
   might do the following:

   .. code-block:: php
      :linenos:

      $smarty->assign('pages', $paginator->getPages());

   You could then access paginator values from a template like so:

   .. code-block:: php
      :linenos:

      {$pages->pageCount}

.. _zend.paginator.usage.rendering.example-controls:

Example pagination controls
^^^^^^^^^^^^^^^^^^^^^^^^^^^

The following example pagination controls will hopefully help you get started:

Search pagination:

.. code-block:: php
   :linenos:

   <!--
   See http://developer.yahoo.com/ypatterns/pattern.php?pattern=searchpagination
   -->

   <?php if ($this->pageCount): ?>
   <div class="paginationControl">
   <!-- Previous page link -->
   <?php if (isset($this->previous)): ?>
     <a href="<?php echo $this->url(array('page' => $this->previous)); ?>">
       < Previous
     </a> |
   <?php else: ?>
     <span class="disabled">< Previous</span> |
   <?php endif; ?>

   <!-- Numbered page links -->
   <?php foreach ($this->pagesInRange as $page): ?>
     <?php if ($page != $this->current): ?>
       <a href="<?php echo $this->url(array('page' => $page)); ?>">
           <?php echo $page; ?>
       </a> |
     <?php else: ?>
       <?php echo $page; ?> |
     <?php endif; ?>
   <?php endforeach; ?>

   <!-- Next page link -->
   <?php if (isset($this->next)): ?>
     <a href="<?php echo $this->url(array('page' => $this->next)); ?>">
       Next >
     </a>
   <?php else: ?>
     <span class="disabled">Next ></span>
   <?php endif; ?>
   </div>
   <?php endif; ?>

Item pagination:

.. code-block:: php
   :linenos:

   <!--
   See http://developer.yahoo.com/ypatterns/pattern.php?pattern=itempagination
   -->

   <?php if ($this->pageCount): ?>
   <div class="paginationControl">
   <?php echo $this->firstItemNumber; ?> - <?php echo $this->lastItemNumber; ?>
   of <?php echo $this->totalItemCount; ?>

   <!-- First page link -->
   <?php if (isset($this->previous)): ?>
     <a href="<?php echo $this->url(array('page' => $this->first)); ?>">
       First
     </a> |
   <?php else: ?>
     <span class="disabled">First</span> |
   <?php endif; ?>

   <!-- Previous page link -->
   <?php if (isset($this->previous)): ?>
     <a href="<?php echo $this->url(array('page' => $this->previous)); ?>">
       < Previous
     </a> |
   <?php else: ?>
     <span class="disabled">< Previous</span> |
   <?php endif; ?>

   <!-- Next page link -->
   <?php if (isset($this->next)): ?>
     <a href="<?php echo $this->url(array('page' => $this->next)); ?>">
       Next >
     </a> |
   <?php else: ?>
     <span class="disabled">Next ></span> |
   <?php endif; ?>

   <!-- Last page link -->
   <?php if (isset($this->next)): ?>
     <a href="<?php echo $this->url(array('page' => $this->last)); ?>">
       Last
     </a>
   <?php else: ?>
     <span class="disabled">Last</span>
   <?php endif; ?>

   </div>
   <?php endif; ?>

Dropdown pagination:

.. code-block:: php
   :linenos:

   <?php if ($this->pageCount): ?>
   <select id="paginationControl" size="1">
   <?php foreach ($this->pagesInRange as $page): ?>
     <?php $selected = ($page == $this->current) ? ' selected="selected"' : ''; ?>
     <option value="<?php
           echo $this->url(array('page' => $page));?>"<?php echo $selected ?>>
       <?php echo $page; ?>
     </option>
   <?php endforeach; ?>
   </select>
   <?php endif; ?>

   <script type="text/javascript"
        src="http://ajax.googleapis.com/ajax/libs/prototype/1.6.0.2/prototype.js">
   </script>
   <script type="text/javascript">
   $('paginationControl').observe('change', function() {
       window.location = this.options[this.selectedIndex].value;
   })
   </script>

.. _zend.paginator.usage.rendering.properties:

Listing of properties
^^^^^^^^^^^^^^^^^^^^^

The following options are available to pagination control view scripts:

.. _zend.paginator.usage.rendering.properties.table:

.. table:: Properties available to view partials

   +----------------+-------+-------------------------------------------------------+
   |Property        |Type   |Description                                            |
   +================+=======+=======================================================+
   |first           |integer|First page number (i.e., 1)                            |
   +----------------+-------+-------------------------------------------------------+
   |firstItemNumber |integer|Absolute number of the first item on this page         |
   +----------------+-------+-------------------------------------------------------+
   |firstPageInRange|integer|First page in the range returned by the scrolling style|
   +----------------+-------+-------------------------------------------------------+
   |current         |integer|Current page number                                    |
   +----------------+-------+-------------------------------------------------------+
   |currentItemCount|integer|Number of items on this page                           |
   +----------------+-------+-------------------------------------------------------+
   |itemCountPerPage|integer|Maximum number of items available to each page         |
   +----------------+-------+-------------------------------------------------------+
   |last            |integer|Last page number                                       |
   +----------------+-------+-------------------------------------------------------+
   |lastItemNumber  |integer|Absolute number of the last item on this page          |
   +----------------+-------+-------------------------------------------------------+
   |lastPageInRange |integer|Last page in the range returned by the scrolling style |
   +----------------+-------+-------------------------------------------------------+
   |next            |integer|Next page number                                       |
   +----------------+-------+-------------------------------------------------------+
   |pageCount       |integer|Number of pages                                        |
   +----------------+-------+-------------------------------------------------------+
   |pagesInRange    |array  |Array of pages returned by the scrolling style         |
   +----------------+-------+-------------------------------------------------------+
   |previous        |integer|Previous page number                                   |
   +----------------+-------+-------------------------------------------------------+
   |totalItemCount  |integer|Total number of items                                  |
   +----------------+-------+-------------------------------------------------------+



.. _`IteratorAggregate`: http://www.php.net/~helly/php/ext/spl/interfaceIteratorAggregate.html