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Lorna Jane Mitchell Lorna Jane Mitchell
Software Engineer
 Zend PHP5 Certified Engineer
Lorna is a software engineer at our London office, although she mostly telecommutes from her home in Leeds. In addition to application development, she designs and delivers training for some of our UK customers, and is an expert on source control. Somehow, she also finds the time to organise the PHPNW Conference and to represent phpwomen.org in Europe.

Monday, December 1. 2008

Zend_Paginator: First Impressions

I have been working on a fun project recently which is built on Zend Framework. While looking at options for paginating a large result set, I came across a Zend Framework module called Zend_Paginator ... and it does just what it says on the tin!

The idea of this module is to allow collections of data to be paginated. It takes the set, restricts the results, and can also generate the page numbers you need to move around between the resulting paginated data. Basically it saves me writing the same pagination code multiple times and then having to fix the bug where the last result on the previous page appears on the next ... all this has been thought of already.

The best way to illustrate this component is I think with a code example. Firstly here's a piece from the controller:

PHP:

<?php

$table = new UserTable();
$users = $table->fetchAll();

$paginator = Zend_Paginator::factory($users);
$paginator->setItemCountPerPage(25);
$paginator->setCurrentPageNumber($this->_request->getParam('page'));

$this->view->users = $paginator;

?>



This sets up the data collection itself, then initialises Zend_Paginator to operate on this data collection. The Zend_Paginator object is then passed to the view rather than passing the data collection itself. In the view, we use our collection in the usual way, something like this (using a smarty view object):

PHP:

<?php

<h1>Users</h1>
<ul>
{foreach from=$this->users item=user}
  <li><a href="/user/profile/id/{$user->user_id}">{$user->getName()}</a></li>
{/foreach}
</ul>

?>



This will show the list of users, but only the first page worth. Adding a call to the pagination control view helper will add the page numbers, for example:

PHP:

<?php

$this->paginationControl($this->users, 'All', 'pagination.tpl');

?>



This renders the page numbers relevant to the specified paginator object using the template you specify in the third argument. The examples on the Zend_Paginator documentation use HTML but it was simple to adapt to using smarty instead, here's my page numbers template:

PHP:

<?php

{if $this->pageCount > 1}
<div class="paginationControl">

{* previous *}
{if isset($this->previous)}
  <a href="{$page_url}/page/{$this->previous}">previous</a>
{else}
  <span class="disabled">previous</span>
{/if}

{* numbered this *}
{foreach from=$this->thisInRange item=page}
{if $page eq $this->current}
{$page}
{else}
<a href="{$page_url}/page/{$page}">{$page}</a>
{/if}
{/foreach}

{* next *}
{if isset($this->next)}
  <a href="user/index/page/{$this->next}">next</a>
{else}
  <span class="disabled">next</span>
{/if}
</div>
{/if}

?>



This has page numbers appearing and the links will actually work - the controller picks this up where it does the getParam for page, so everything should automagically work at this point. This component is a good timesaver, next time you are displaying multiple records with Zend Framework, you may consider trying it out.
Posted by Lorna Jane Mitchell at 15:15 | Comments (12) | Trackback (1)
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Zend_Paginator on Ibuildings Blog
In case anyone thought it was a bit quiet around here - that's because I've been working on a few other bits and pieces! Today I posted an article about Zend_Paginator to the Ibuildings blog. Do stop by and have a read - and read the comments as well as
Weblog: LornaJane
Tracked: Dec 01, 18:41

Comments
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Hi Lorna,

By calling the fetchAll() method, you will fetch the whole resultset into an array, which will give you a significant performance decrease with a large resulset.

The DbSelect adapter for Zend_Paginator has a nice feature where it will automaticly add a limit clause to your query, in such way that it would only query the records that you actually need.

Here's an example:

CODE:
// ...
$select = $db->from('users')->order('name');

$paginator = new Zend_Paginator(new Zend_Paginator_Adapter_DbSelect($select));
$paginator->setCurrentPageNumber($this->_getParam('page', 1));
$paginator->setItemCountPerPage(25);
$this->view->paginator = $paginator;


I hope this makes sense :-)! Good luck! :-)
#1 Andries Seutens (Homepage) on 2008-12-01 15:45 (Reply)
I also writed a Doctrine adapter that make Zend_Paginator operate on a Doctrine_Collection object; the zf component is really versatile and the included adapter cover arrays, zend_db_select and instances of Iterator.
#2 Piccolo Principe on 2008-12-01 17:41 (Reply)
it's possible to have look at this adapter? it seems interesting
#2.1 ftb on 2008-12-01 18:31 (Reply)
http://ossigeno.svn.sourceforge.net/viewvc/ossigeno/trunk/core/library/Otk/Paginator/Adapter/
Any suggestion is appreciated.
#2.1.1 Piccolo Principe on 2008-12-01 23:14 (Reply)
Ok grazie!
#2.1.1.1 ftb on 2008-12-02 20:36 (Reply)
Why not use Doctrine_Pager?
#2.2 Edgar on 2008-12-02 14:25 (Reply)
Because as a Unix guy I beware of tools that does too much, so I integrated Doctrine in my project for Domain Modelling, and not for other purposes; and because my views already use a Zend_Paginator instance.
Also Doctrine has giant static clings and I tend to wrap it in helpers or classes the more I can.
#2.2.1 Piccolo Principe on 2008-12-02 14:32 (Reply)
PEAR has had a paging class for years - Pager. Imaginitive name eh...? :-)
#3 Richard Heyes (Homepage) on 2008-12-01 18:00 (Reply)
BTW, you can use Zend_Paginator regardless of whether you're working on a "Zend Framework" project (which really is really not a black/white thing in the world of ZF anyways). Use-at-will architecture can come in handy sometimes. :-)
Great article.

,Wil
#4 Wil Sinclair (Homepage) on 2008-12-01 19:00 (Reply)
Lorna, as Andries already mentioned, fetching the whole resultset is not efficient at all.

Here's an article I wrote a couple of years ago on the topic (using PEAR::Pager, yes, I'm biased :-D):

http://www.alberton.info/pear_pager_tutorial_database_results.html

I even found a little test I ran in 2004 comparing the two approaches ("fetch the full resultset and then paginate" Vs. "limit the resultset up front"). Since an image is worth a thousand words, have a look at the db load: the peaks in the image refer to a limit_query => full_query => limit_query => full_query sequence.

http://www.alberton.info/images/pager-db-resultset-load.jpg

The spike due to having to limit the query is a bit higher, because the DBMS has to filter the records, but the overall load is usually a lot lighter and the resources are freed sooner.

The performance hit becomes really an issue if you use buffered queries and/or the resultset is transferred over a network.

HTH
#5 Lorenzo Alberton (Homepage) on 2008-12-01 21:28 (Reply)
I use the pagination class from this site:

PHP pagination class

Very flexible as it does just that, return an array of values to handle the rows display. Blends well
with current frameworks or coding styles. Not to mention that by the looks of it's very fast.

But if you are already on a commercial framework you should stick with the classes it offers.
#6 Michael on 2008-12-03 19:20 (Reply)
Hi Lorna,

I hope you help me solve this problem with Zend Paginator. My problem is that I want to use paginator in 2 times, first I let it at the top of the webpage, the second is at the bottom of the webpage. But it caused an error and if I use it one time, and let it at the top or the bottom, everything works. So I don't know how to fix it.

Please help me. Thank you very much
#7 Thuong on 2008-12-16 08:53 (Reply)

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