Posted by Jeremy on 10/22/07 22:37

Weston wrote:
> Poking around with XPath using SimpleXML, it looks like there are at
> least a few reasonably common XPath operators and predicates that
> aren't supported. I'd like to check my observations against other
> people's experience, and find out if I'm missing something.
>
> Here's what it looks like to me in PHP 5.2.0:
>
> * the count() predicate seems to fail quietly (no error or warning,
> you just receive a false value from the xpath method rather than an
> array)
> * the "|" (union) operator seems to also fail quietly by returning an
> empty array
> * the "union" operator seems to cause an error
> * the "intersect" operator also causes an error (and needless to say,
> with | and count() not working, using something like the Kaysian
> technique to get the intersection won't work)
>
> Does this accurately capture the current state of things?
>
> If so, are the bulk of developers simply not using these features, or
> are they instead writing around the missing features in PHP rather
> than trying to get XPath to do the work?
>
> Or is there a better option?
>

AFAIK, the various PHP API's (SimpleXML, DOM) use libxml as a backend,
without much logic in between. So if the XPath operators are supported
by libxml, they ought to be supported by PHP. If they're not supported
by libxml, that would really surprise me.

That said, try using the DOM API instead of SimpleXML and see if you
have better results. Then, try peeking into the libxml error stack
directly using the libxml functions:

http://us.php.net/manual/en/ref.libxml.php

Jeremy

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