A Sneak Preview of XML in PHP 5

Adam TrachtenbergCo-Author PHP Cookbook

adam@trachtenberg.com

January 21, 2004

Adam Trachtenberg [http://www.trachtenberg.com]

XML Extensions in PHP 5• Work together as a unified whole.• Are standardized on a single XML

library: libxml2.• Fully comply with W3 specifications.• Efficiently process data.• Provide you with the right XML tool for

your job.

Adam Trachtenberg [http://www.trachtenberg.com]

Five Major Extensions• DOM• SAX• SimpleXML• XPath• XSLT

Adam Trachtenberg [http://www.trachtenberg.com]

Music Catalogue XML<music> <artist id="1"> <name>The Rolling Stones</name> <albums> <title>Exile On Main Street</title> </albums> </artist> <artist id="2"> <name>Aimee Mann</name> <albums> <title>I'm With Stupid</title> <title>Bachelor No. 2</title> </albums> </artist></music>

Adam Trachtenberg [http://www.trachtenberg.com]

DOM• The 800 pound gorilla of XML.• You can do everything and the <kitchen:sink> with DOM, but navigating through your documents can be cumbersome.

• Tree-based API• Undergone a complete rewrite to

correspond with DOM specifications.

Adam Trachtenberg [http://www.trachtenberg.com]

DOM Example Code$music = new domDocument;$music->preserveWhiteSpace = false;$music->load('music.xml');

$names = $music->    getElementsByTagName('name');foreach ($names as $name) {  print $name->firstChild

->nodeValue;}

The Rolling StonesAimee Mann

Adam Trachtenberg [http://www.trachtenberg.com]

SAX• PHP's original XML extension.• Streaming (or event-based) parser• Uses less memory than DOM, but

frequently at the expense of more complex PHP code.

• Used to use expat. Now uses libxml2

Adam Trachtenberg [http://www.trachtenberg.com]

SimpleXML• A new PHP 5 only extension.• Excels at parsing RSS files, REST results,

and configuration data.• If you know the document's format ahead

of time, SimpleXML is the way to go.• Only supports elements, text nodes, and

attributes.• Tree-based API

Adam Trachtenberg [http://www.trachtenberg.com]

SimpleXML Example Code$x = simplexml_load_string($xml);$artists = $x->artist;

foreach($artists as $artist) {    print "$artist->name\n";}

The Rolling StonesAimee Mann

Adam Trachtenberg [http://www.trachtenberg.com]

XPath• Query XML documents like you're using

regular expressions to find the subset of information that you need and eliminate the unnecessary portions.

• Highly useful and undervalued piece of XML.

• Usable with DOM and SimpleXML

Adam Trachtenberg [http://www.trachtenberg.com]

XPath Example Code$xpath = new domXPath($music);$albums = $xpath->query("/music/artist[name =

'Rolling Stones']/albums/name");

foreach ($albums as $a)print $a->firstChild->nodeValue;

}Exile On Main Street

Adam Trachtenberg [http://www.trachtenberg.com]

XSLT• A way to take XML documents and

transform them into HTML or another output format.

• Defines templates using XML-based stylesheets.

• Easily shared among different applications, but has a quirky syntax.

• Uses libxslt library instead of Sablotron.

Adam Trachtenberg [http://www.trachtenberg.com]

XSLT Example Code$xslt = new xsltProcessor;$xsl = domDocument::load('music.xsl');

$xslt->importStylesheet($xsl);

$xml = domDocument::load('music.xml');

print $xslt->transformToXML($xml);

Adam Trachtenberg [http://www.trachtenberg.com]

Web Services• SOAP

– PEAR::SOAP– soap Extension (Written in C)

• REST– SimpleXML

• XML-RPC– Still there…

Adam Trachtenberg [http://www.trachtenberg.com]

Resources• DOM, XSLT, XPath

– PHP 5 Meets XML and the DOMPHP Magazine: www.php-mag.net

• SimpleXML– Using PHP 5's SimpleXML

O’Reilly Network: www.onlamp.com/php

Adam Trachtenberg [http://www.trachtenberg.com]

Did I mention I wrote a book?