1. #PBCAT
The Lumberjack - Xpath 101
Thomas Weinert

2. About Me
● Application Developer
● PHP
● JavaScript
● XSL
● papaya Software GmbH
● papaya CMS
● Technical Director
● FluentDOM

3. Questions!
Please ask any time!

4. Xpath 1
● XML Path Language
● W3C Recommendation 16 November 1999
● Used by
● XSLT 1
● XPointer

5. Xpath 2
● W3C Recommendation 23 January 2007
● Superset of Xpath 1
● More data types

6. DOM
● Document Object Modell
● Standard extension: ext/dom
● LibXml2
● Xpath 1

7. DOMXpath
● Create after loading the document!
● evaluate()/query()
<?php
$str = '<sample><element/></sample>';
$dom = new DOMDocument();
$dom->loadXML($str);
$xpath = new DOMXPath($dom);
var_dump($xpath->evaluate('//element'));
var_dump($xpath->evaluate('//noelement'));
var_dump($xpath->evaluate('//noelement/@attr'));
?>
object(DOMNodeList)[5]

8. SimpleXML
● Always return SimpleXML
<?php
$str = '<sample><element/></sample>';
$xml = simplexml_load_string($str);
var_dump($xml->xpath('//element'));
var_dump($xml->xpath('//noelement'));
var_dump($xml->xpath('//noelement/@attr'));
?>
array array boolean false
0 => empty
object(SimpleXMLElement)[2]

9. XSL
● Libxslt
● based on Libxml2
● ext/xsl
● ext/xslcache

10. Syntax
/element/child[@attr]
Absolute Path Step 1 Predicate
Separator Step 2

11. Nodes
● node()
● * or qualified-name
● text()
● comment()
● processing-instruction()

12. Axes
● axis::...
● Full syntax
● Short Syntax
● Default Axis

13. child
<barcamps>
<barcamp title="PHP Unconference Hamburg" id="phpuchh">
<link href="http://www.php-unconference.de/" />
</barcamp>
<barcamp title="PHP Barcamp Salzburg" id="phpbcat">
<link href="http://www.phpbarcamp.at/cms/" />
<speakers-featured>
<speaker>Bastian Feder</speaker>
</speakers-featured>
<speakers>
<speaker>Thomas Weinert</speaker>
</speakers>
</barcamp>
<barcamp title="PHP Unconference Europe" id="phpuceu">
<link href="http://www.phpuceu.org/">
</barcamp>
</barcamps>

14. descendant
<barcamps>
<barcamp title="PHP Unconference Hamburg" id="phpuchh">
<link href="http://www.php-unconference.de/" />
</barcamp>
<barcamp title="PHP Barcamp Salzburg" id="phpbcat">
<link href="http://www.phpbarcamp.at/cms/" />
<speakers-featured>
<speaker>Bastian Feder</speaker>
</speakers-featured>
<speakers>
<speaker>Thomas Weinert</speaker>
</speakers>
</barcamp>
<barcamp title="PHP Unconference Europe" id="phpuceu">
<link href="http://www.phpuceu.org/">
</barcamp>
</barcamps>

15. parent
<barcamps>
<barcamp title="PHP Unconference Hamburg" id="phpuchh">
<link href="http://www.php-unconference.de/" />
</barcamp>
<barcamp title="PHP Barcamp Salzburg" id="phpbcat">
<link href="http://www.phpbarcamp.at/cms/" />
<speakers-featured>
<speaker>Bastian Feder</speaker>
</speakers-featured>
<speakers>
<speaker>Thomas Weinert</speaker>
</speakers>
</barcamp>
<barcamp title="PHP Unconference Europe" id="phpuceu">
<link href="http://www.phpuceu.org/">
</barcamp>
</barcamps>

16. following-sibling
<barcamps>
<barcamp title="PHP Unconference Hamburg" id="phpuchh">
<link href="http://www.php-unconference.de/" />
</barcamp>
<barcamp title="PHP Barcamp Salzburg" id="phpbcat">
<link href="http://www.phpbarcamp.at/cms/" />
<speakers-featured>
<speaker>Bastian Feder</speaker>
</speakers-featured>
<speakers>
<speaker>Thomas Weinert</speaker>
</speakers>
</barcamp>
<barcamp title="PHP Unconference Europe" id="phpuceu">
<link href="http://www.phpuceu.org/">
</barcamp>
</barcamps>

17. More Axes
● ancestor ● attribute
● ancestor-or-self ● namespaces
● descendant-or-self
● following
● preceding
● preceding-sibling
● self

18. Short Syntax
● self::node()/
descendant-or-self::node()/
child::para
● .//para
Axis Short
child
self .
parent ..
attribute @
descendant-or-self /

19. Cast Functions
● string()
● number()
● boolean()
echo $xpath->evaluate('string(/html/head/title)');

20. Node Functions
● count() ● name()
● last() ● local-name()
● position() ● namespace-uri()
$list = $xpath->evaluate(
'//*[local-name() = 'li' and position() = last()]'
);

21. String Functions
● concat() ● normalize-string()
● starts-with() ● translate()
● contains()
● substring-before()
● substring-after()
● substring()
● string-length()

22. Match A Class
● normalize-string()
● concat()
● contains()

23. Namespaces
● URN
● Prefix
● Default Namespace
● Own Prefixes
● Attributes

24. Bug #49490
● Namespace prefix conflict
$dom = new DOMDocument();
$dom->loadXML(
'<foobar><a:foo xmlns:a="urn:a">'.
'<b:bar xmlns:b="urn:b"/></a:foo>'.
'</foobar>'
);
$xpath = new DOMXPath($dom);
$context = $dom->documentElement->firstChild;
$xpath->registerNamespace('a', 'urn:b');
var_dump(
$xpath->evaluate('descendant-or-self::a:*', $context)
->item(0)->tagName
);

25. Tools
● Firebug
● Firefox AddOns

26. CSS Selectors
● JavaScript libraries
● element nodes
● *
● no axes
● descendant-or-self::*
● can ignore namespaces
● descendant-or-self::*[local-name() = '...']

27. Thanks
● Web:
● http://www.papaya-cms.com/
● http://www.a-basketful-of-papayas.net/
● Twitter
● @ThomasWeinert
● Joind.in
● http://joind.in/1621