Using DOMDocument PHP classes on simple XML file - php

Question

My XML document is as follows.
<?xml version="1.0" encoding="utf-8"?>
<userSettings>
<tables>
<table id="supertable">
<userTabLayout id="A">{"id":"colidgoeshereX"}</userTabLayout>
<userTabLayout id="B">{"id":"colidgoeshereY"}</userTabLayout>
</table>
<table id="almost-supertable">
<userTabLayout id="A">{"id":"colidgoeshereC"}</userTabLayout>
<userTabLayout id="B">{"id":"colidgoeshereD"}</userTabLayout>
</table>
</tables>
</userSettings>
I'm using the following PHP code to load the file (DOMDocument) and then DomXpath to traverse the document
<?php
...
$xmldoc = new DOMDocument();
$xmldoc->load ($filename);
$xpath = new DomXpath($xmldoc);
$x = $xpath->query("//tables/table");
$y = $x->item(0);
...
?>
The $y variable now contains a DOMElement object, with a nodeValue attribute containing the string as follows:
["nodeValue"]=>
string(81) "
{"id":"colidgoeshereX"}
{"id":"colidgoeshereY"}
"
My question is, what happened to the <userTabLayout> node? Why do I not see this as a child node to the <table> node? And if I wanted to access the <userTabLayout id="B"> node, how would I do that?
Normally I'd read the documentation on this kind of stuff, but the official documentation on the official PHP page, is really sparse.

Answer 1

My question is, what happened to the <userTabLayout> node?
Nothing happened to it. The <userTabLayout> elements are child-elements of the DOMElement you have in $y.
Why do I not see this as a child node to the <table> node?
Because you're not looking for child-nodes by using the nodeValue field.
And if I wanted to access the <userTabLayout id="B"> node, how would I do that?
By traversing the document, e.g. accessing the child nodes via the childNodes field (surprise).
Normally I'd read the documentation on this kind of stuff, but the official documentation on the official PHP page, is really sparse.
That's because the DOM is documented by the W3C already, e.g. here: http://www.w3.org/TR/1998/REC-DOM-Level-1-19981001/
As that link is specification it might be a bit technical, so harder to work into, however you can consider it complete (e.g. check for realness if you need to know it). Once understanding that DOM is specified, you can related to any DOM documentation available, for example within MDN, even in Javascript (one of the two default implementations by W3C), it works similar in PHP (esp. for traversal or how Xpath works).
Have fun reading!

Answer 2

Well, you can work without the DomXpath.
$xmlS = '
<userSettings>
<tables>
<table id="supertable">
<userTabLayout id="A">{"id":"colidgoeshereX"}</userTabLayout>
<userTabLayout id="B">{"id":"colidgoeshereY"}</userTabLayout>
</table>
<table id="almost-supertable">
<userTabLayout id="A">{"id":"colidgoeshereC"}</userTabLayout>
<userTabLayout id="B">{"id":"colidgoeshereD"}</userTabLayout>
</table>
</tables>
</userSettings>
';
$xmldoc = new DOMDocument();
$xmldoc->loadXml($xmlS);
$table1 = $xmldoc->getElementsByTagName("tables")->item(0);
$userTabLayoutA = $table1->getElementsByTagName("userTabLayout")->item(0);
$userTabLayoutB = $table1->getElementsByTagName("userTabLayout")->item(1);
echo $userTabLayoutA->nodeValue; // {"id":"colidgoeshereX"}
echo $userTabLayoutB->nodeValue; // {"id":"colidgoeshereY"}
As you can see, you can access all elements, one by one, using getElementsByTagName and specifying what item do you want.