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These parameters you provide when creating an object are passed to the class

constructor

upon object

creation. The constructor is a special method inside the class that gets called automatically when the

object is created. You use it to set up some things based on the parameters. In this case, when creating

an

RSSFactory

object, you pass the feed title, link, and description. These are the attributes that are

associated with the overall feed itself, not its individual elements. The constructor definition looks like

this, in the

RSSFactory

class:

// the class constructor is executed when creating an instance of the class

function RSSFactory($title, $link, $description,

$language = ‘en-us’, $items = array())

{

// save feed data to local class members

$this->_title = $title;

$this->_link = $link;

$this->_description = $description;

$this->_language = $language;

$this->_items = $items;

}

So the constructor saves the parameter values to its properties, setting the object’s state. Note the usage of

$this

, which means “the current class instance” when used inside a class. (If you create more objects of

type

RSSFactory

, the

$this

reference in each of those objects will be different.)

Back in

feed.php

, after the

$rss_feed

object is created, its

addItem

method is called twice to add two

feed items:

// create feed

$rss_feed = new RSSFactory(‘SEOEgghead.com New Products Feed’,

‘http://www.seoegghead.com/seo-with-php-updates.html’,

‘Exciting new products, updated daily’);

// add feed item

$rss_feed->addItem(‘New Link Juice with Orange Flavor!’,

‘http://localhost/seophp/Products/SEO-Toolbox-C6/Link-Juice-P31.html’,

‘The new Link Juice product of SEOEgghead.com can do wonders for your website!’);

// add feed item

$rss_feed->addItem(‘Enhance Your PHP Applications with AJAX!’,

‘http://seophp.example.com/Products/Friends-Shed-C2/AJAX-PHP-Book-P42.html’,

‘Check out this AJAX tutorial for PHP developers!’);

Finally, the

get()

method is called to echo the RSS feed structure. The output of this particular exercise

will be as follows:

<rss version=”2.0”>

<channel>

<title>SEOEgghead.com New Products Feed</title>

<link>http://www.seoegghead.com/new-products.html</link>

<description>Exciting new products, updated daily</description>

<item>

<title>New Exciting Product</title>

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Chapter 7: Web Feeds and Social Bookmarking

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