CHAPTER 8 – XML with PHP 5 – XML_RSS

RSS (RDF Site Summary, Really Simple Syndication) feeds are a common use of XML. RSS is an XML vocabulary to describe news items, which can then be integrated (also called content syndication) into your own web site. PHP.net has an RSS feed with the latest news items at http://www.php.net/news.rss. You can find the dry specs of the RSS specification at http://web.resource.org/ rss/1.0/spec, but it's much better to see an example. Here is part of the RSS file we're going to parse: <?xml version="1.0" encoding="UTF-8"?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://purl.org/rss/1.0/" xmlns:dc="http://purl.org/dc/elements/1.1/" > <channel rdf:about="http://www.php.net/"> <title>PHP: Hypertext Preprocessor</title> <link>http://www.php.net/</link> <description>The PHP scripting language web site</description> <items> <rdf:Seq> <rdf:li rdf:resource="http://qa.php.net/" /> <rdf:li rdf:resource="http://php.net/downloads.php" /> </rdf:Seq> </items> </channel>  <item rdf:about="http://qa.php.net/"> <title>PHP 4.3.5RC1 released!</title> <link>http://qa.php.net/</link> <description>PHP 4.3.5RC1 has been released for testing. This is the first release candidate and should have a very low number of problems and/or bugs. Nevertheless, please download and test it as much as possible on real-life applications to uncover any remaining issues. List of changes can be found in the NEWS file.</description> <dc:date>2004-01-12</dc:date> </item> <item rdf:about="http://www.php.net/downloads.php"> <title>PHP 5.0 Beta 3 released!</title> <link>http://www.php.net/downloads.php</link> <description>PHP 5.0 Beta 3 has been released. The third beta of PHP is also scheduled to be the last one (barring unexpected surprises). This beta incorporates dozens of bug fixes since Beta 2, better XML support and many other improvements, some of which are documented in the ChangeLog. Some of the key features of PHP 5 include: PHP 5 features the Zend Engine 2. XML support has been completely redone in PHP 5, all extensions are now focused around the excellent libxml2 library (http://www.xmlsoft.org/). SQLite has been bundled with PHP. For more information on SQLite, please visit their website. A new SimpleXML extension for easily accessing and manipulating XML as PHP objects. It can also interface with the DOM extension and vice-versa. Streams have been greatly improved, including the ability to access low-level socket operations on streams.<description><dc:date>2003-12-21< dc:date> </item>  </rdf:RDF> This RSS files consists of two parts: the header, describing the site from which the content is syndicated, and a list of available items. The second part consists of the news items. We don't want to refetch the RSS file from http:// php.net every time a user visits a page that displays this information. Thus, we're going to add some caching. Downloading the file once a day should be sufficient because news isn't updated more often than daily. (On php.net, other sites might have different policies.) We're going to use the PEAR::XML_RSS class that we installed with pear install XML_RSS. Here is the script: <?php require_once "XML/RSS.php"; $cache_file = "/tmp/php.net.rss"; First, as shown previously, we include the PEAR class and define the loca- tion of our cache file: if (!file_exists($cache_file) || (filemtime($cache_file) < time() - 86400)) { copy("http://www.php.net/news.rss", $cache_file); } Next, we check whether the file has been cached before and whether the cache file is too old (86,400 seconds is one day). If it doesn't exist or is too old, we download a new copy from php.net and store it in the cache file: $r =& new XML_RSS($cache_file); $r->parse(); We instantiate the XML_RSS class, passing our RSS file, and call the parse() method. This method parses the RSS file into a structure that can be fetched by other methods, such as getChannelInfo() that returns an array con- taining the title, description, and link of the web site, as shown here: array(3) { ["title"]=> string(27) "PHP: Hypertext Preprocessor" ["link"]=> string(19) "http://www.php.net/" ["description"]=> string(35) "The PHP scripting language web site" } getItems() returns the title, description, and link of the news item. In the following code, we use the getItems() method to loop over all items and display them: foreach ($r->getItems() as $value) { echo strtoupper($value['title']). "n"; echo wordwrap($value['description']). "n"; echo "t{$value['link']}nn"; } ?> When you run the script, you will see that it outputs the news items from the RSS file: PHP 4.3.5RC1 RELEASED! PHP 4.3.5RC1 has been released for testing. This is the first release candidate and should have a very low number of problems and/or bugs. Nevertheless, please download and test it as much as possible on real-life applications to uncover any remaining issues. List of changes can be found in the NEWS file. http://qa.php.net/ PHP 5.0 BETA 3 RELEASED! PHP 5.0 Beta 3 has been released. The third beta of PHP is also scheduled to be the last one (barring unexpected surprises). This beta incorporates dozens of bug fixes since Beta 2, better XML support and many other improvements, some of which are documented in the ChangeLog. Some of the key features of PHP 5 include: PHP 5 features the Zend Engine 2. XML support has been completely redone in PHP 5, all extensions are now focused around the excellent libxml2 library (http://www.xmlsoft.org/). SQLite has been bundled with PHP. For more information on SQLite, please visit their website. A new SimpleXML extension for easily accessing and manipulating XML as PHP objects. It can also interface with the DOM extension and vice-versa. Streams have been greatly improved, including the ability to access low-level socket operations on streams. http://www.php.net/downloads.php

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