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Why?

PHP's SimpleXML extension is a powerfully simple way of accessing and manipulating XML documents in a "PHP-ish" way. But although using it feels like using a PHP object, there is an awful lot of magic that enables it to work that way, which is poorly documented, and poorly understood.

One of the key mistakes people make when working with SimpleXML is to reach for the familiar debug outputs: print_r, var_dump, var_export. But none of these work because a SimpleXML object isn't a real PHP object - it's just a wrapper around a lower-level XML parser.

Rule number 1 of SimpleXML: You do not print_r SimpleXML

So the obvious question is: What do I use instead when I want to inspect my SimpleXML objects? This project aims to be the answer to that question.

What?

  • The first piece of this project is a simple function - simplexml_dump() - which echoes a basic summary of any SimpleXMLElement object you give it.
  • Early feedback from users on StackOverflow was that a fully recursive function would be useful, although this would obviously need to do something different from an XML pretty-printer. The next function is therefore simplexml_tree() which shows an entire XML structure in summarised tree form. The output is designed to show exactly what operators and methods are needed to access each node shown.

Features

Read the PHPDoc, and try it out, to see exactly how it works but to give you a taste:

  • Can display any of the varieties of object produced while navigating a SimpleXML structure: single elements, lists of elements, single attributes, lists of attributes.
  • Displays the namespace alias and URI of the current element, and all its direct children.
  • Lists the total number and name of all attributes on an element (broken down by namespace).
  • Lists the total number of direct children (broken down by namespace) along with a summary of their names (e.g. the fact that there are 500 Result elements and 1 Info element).
  • Shows complete string content of a node, including CDATA.

Limitations and Warnings

  • There is currently no way of distinguishing between a single element (e.g. $sxml->Result[0]) and a list of elements (e.g. $sxml->Result or $sxml->children()) which happens to include only one item. They can however behave differently - foreach ( $sxml->Result[0] as $result ) is equivalent to foreach ( $sxml->Result[0]->children() as $result ).
  • The xpath() method doesn't return a SimpleXMLElement, but an actual array of objects. simplexml_dump() will currently return an error if you try to pass it this array.
  • Namespace handling is somewhat tricky, and there may be edge-cases which are not handled correctly.

Who?

This project was originated by Rowan Collins, AKA IMSoP. My homepage is at http://rwec.co.uk, and you can reach me by e-mail on the obvious addresses @ that domain.

The code here is free to use for any purpose whatsoever, but with a polite request that you treat it like Free Software, and a strong request that you don't pass it off as your own. I'm happy for you to take it away, improve it, use it for whatever you like, but I'd like you to credit me as the originator. I'd also be more than happy to hear what you do with it, and how you've improved on it.