The Bakery Everything CakePHP

Please be sure you are familiar with the basics of Cake pagination. This information can be found in the basic CakePHP pagination tutorial.

This tutorial is going to be a work in progress though. There are likely some "best practices" I am not familiar with. I would like to compile a fairly good amount of "best practices" into this tutorial. I am sure the many smart people in the Cake community will help out as they find opportunity to give input.

Ok let's get started. First we will go through an Ajax pagination example. Then after that there will just be a discussion of abstract ideas on pagination techniques.

Ajax Pagination

In reality CakePHP makes pagination with Ajax fairly simple. I'm going to just work with the Customer list from the basic tutorial. Again, your Model does not need to do anything special. So we'll just look at the View and Controller code you will need to implement.

First things first, make sure prototype.js is included by your layout. You can't do any Ajax without the javascript Ajax library. All of my layouts usually looks like this.
Download code <?php if(!empty($ajax)): ?>
    <?php echo $javascript->link('prototype');?>
<?php endif; ?>

You'll have to get your own ajax loader, but your view can look like this.

View Template:

Download code This is the customer listing page. There are many things I might like to put here. Below is a list of all of the customers in the database.
<br /><br />

<div id="LoadingDiv" style="display: none;">
    <?php echo $html->image('ajax-loader.gif'); ?>
</div>

<div id="CustomerPaging">
    <?php echo $this->renderElement('customers/paging'); ?>
</div>

Now the actual paging is happening within an element, you need to make an element. I put my elements within a folder of the name of the controller that uses it. This one is elements/customers/paging.ctp.
Download code <?php
    $paginator->options(
            array('update'=>'CustomerPaging', 
                    'url'=>array('controller'=>'Customers', 'action'=>'display'), 
                    'indicator' => 'LoadingDiv'));
?>

Showing Page <?php echo $paginator->counter(); ?>
<table>
    <tr>
        <th><?php echo $paginator->sort('Name', 'name');?></th>
        <th><?php echo $paginator->sort('Store', 'store');?></th>
    </tr>
<?php foreach($customers as $customer): ?>
    <tr>
        <td><?php echo $customer['Customer']['name']; ?></td>
        <td><?php echo $customer['Customer']['store']; ?></td>
    </tr>
<?php endforeach; ?>
</table>
<?php echo $paginator->prev(); ?> -
<?php echo $paginator->numbers(array('separator'=>' - ')); ?>
<?php echo $paginator->next('Next Page'); ?>

The controller now needs to know when its just a page load, and when it an Ajax call. We use Cake's RequestHandler to accomplish this.

Controller Class:

Download code <?php 
class CustomersController extends Controller {

    var $name = 'Customers';

    var $components = array('RequestHandler');
    
    var $paginate = array('limit' => 15, 'page' => 1, 'order'=>array('name'=>'asc'));

    function display() {
        if(!$this->RequestHandler->isAjax()) {
            // things you want to do on initial page load go here
            $this->pageTitle = "Customer List";    
        }
        
        $this->set('customers', $this->paginate('Customer'));
        
        if($this->RequestHandler->isAjax()) {
            $this->viewPath = 'elements'.DS.'customers';
            $this->render('paging');            
        }
    }
}
?>

Searching

A very common use for pagination is probably search pages. Lets try to find a good technique we can use to implement a paginated search.

The view is going to change just a little. We'll add a form and a text field for the user to enter a search term into.

View Template:

Download code <?php echo $form->create('Customer', array('action'=>'display'))?>

<?php echo $form->text('Customer.search'); ?>
<div id="CustomerPaging">
    <?php echo $this->renderElement('customers/paging'); ?>
</div>

</form>


Now the controller is where things get a little tricky. The paginator won't hold on to the search term for page 2 or page 3 and so forth. So we have to hold onto the search term ourselves and pass it along to the paginator manually. I have used sessions to implement this functionality. Here is how my controller looks.

Controller Class:

Download code <?php 
...
function display() {
    if(!$this->RequestHandler->isAjax()) {
        $this->pageTitle = "Customer List";    
        // clear the session on first page visit
        $this->Session->del($this->name.'.search');
    }
    
    if(!empty($this->data))
        $search = $this->data['Customer']['search'];
    elseif($this->Session->check($this->name.'.search'))
        $search = $this->Session->read($this->name.'.search');

    $filters = array();
    if(isset($search)) {
        $filters = array("lower(Customer.name) like '%".low($search)."%'");
        $this->Session->write($this->name.'.search', $search);        
    }
        
    $this->set('customers', $this->paginate('Customer', $filters));
    
    if($this->RequestHandler->isAjax()) {
        $this->viewPath = 'elements'.DS.'customers';
        $this->render('paging');            
    }
}

...
?>

Other Techniques

Of course there are other things you might want to with pagination. Here are a few other little techniques I've picked up as I've gone along.

Action parameters¹

Lets say you have an action that looks like this..
Download code <?php
...
function display($one=null, $two=null) {
    if(!($one && $two))
        $this->cakeError('error404', array($this->params['url']));
...
?>
You can get the paginator to hold onto parameters $one and $two by using 'url'=>$this->params['pass'] in your options array. Possibly you might want to make it standard to do something along this lines in your views:
Download code <?php
    $paginator->options(
            array('update'=>'CustomerPaging', 
                    'url'=>$this->params['pass'],
                    'model'=>'Customer', 
                    'indicator' => 'LoadingDiv'));
?>

Empty Pagination²

There will likey be a sitution where it would be convenient to get an empty pagination set. That can be accomplished using something like this:
Download code <?php
    $this->set('customers', $this->paginate('Customer', array('id'=>null)));
?>

Known Weaknesses

Cake 1.2 is still in development. I feel obligated to inform the reader of known weaknesses in pagination, before they dive in and start using it. There are only two things I know of which have been any hinderance to anybody.

1. Sorting by another model - Perhaps your model you want to paginate with has a belongsTo relationship to another model. You may want to sort by that other model. Currently this is not possible for security reasons. I'm told it will be done before Cake 1.2 becomes official. For now though, I am sorry you can only sort by the Model you are paginating with.
2. Paginating with Javascript - Perhaps you want to move to page two of your list or sort using some sort of javascript command. Unfortunaltely this is difficult to do right now because the paginator only returns full anchor tags. This is not super hard to hack and get around. Below is a little function I've used to extract the url from a link. Download code <?php $url = preg_replace('/<a\s+.*?href="([^"]+)"[^>]*>([^<]+)<\/a>/is', '\1', $link); ?>

Credits

Quick thanks to ¹Andy Dawson (AD7six), Jitka Koukalova (poLK), and ²Jared Hoyt. The sum of mutiple brains is better than mine is.