Xpath parent selector in PHP - php

Question

A bit of background:
Hi guys,
I'm creating a router in PHP for an MVC application on and decided that the structure would be in XML. I have an XML file containing all valid routes (pages) in the system along with their associated controller & action.
There's also a 'param' to indicate if there's a variable on the end of the URI and the variable name to assign it to (confusingly named I know!!)
What I'm doing is looking at the REQUEST_URI and using PHP's explode function to turn it into an array of 'route' elements which I then build a query for.
Here's some sample XML:
<routes>
<route>
<url>blog</url>
<params>
<controller>blogController</controller>
<action>indexAction</action>
</params>
<route>
<url>entry</url>
<params>
<controller>blogController</controller>
<action>entryAction</action>
<param>entryId</param>
</params>
</route>
</route>
</routes>
And here's the query that's being built:
/routes/route/url[text()="blog"]/../route/url[text()="entry"]/..
This always seems to return 0 nodes in PHPs XPath, but using an online expression tester I get the entry route matched.
Can anyone explain what might be going wrong? Does PHP's Xpath parser understand this syntax? I have also tried the ::parent* method
Cheers!

Answer 1

You shouldn't need .. or parent::*.
Try this instead:
/routes/route[url="blog"]/route[url="entry"]
You shouldn't need text() either, but I also don't know PHP very well. Ff the above doesn't work, try:
/routes/route[url/text()="blog"]/route[url/text()="entry"]

Answer 2

XPath wise I come to the same conclusion like DevNull, only a slight addition to select the first match:
/routes/route[url="blog"]/route[url="entry"][1]
With a object interface:
$routes = new RoutesXML($xml);
var_dump($routes->fromPath('blog/entry')); # The SimpleXMLElement
var_dump($routes->fromPath('blog/entry2')); # NULL
Example Implementation:
class RoutesXML
{
private $xml;
public function __construct($xml) {
$this->xml = simplexml_load_string($xml);
}
public function fromPath($path) {
$expression = '/routes';
foreach(explode('/', $path) as $element)
$expression .= "/route[url='$element']";
$expression .= '[1]';
list($route) = $this->xml->xpath($expression) + array(NULL);
return $route;
}
}