Reading values of a multi-dimensional array populated by xpath - php

Question

I am a bit of a newbie to PHP and I'm not sure what I'm missing here. I have an multidimensional array that I've created from an XML file using XPath. I'm able to move through the array and retrieve most all values but I am getting stuck on one section.
Example of XML structure:
MasterNode
SubNodeItem1
SubNodeItem2
SubNodeItem3
SubNodeItemList
SubListItem
SubItemProperty1
SubItemProperty2
SubItemProperty3
SubItemList
SubItemProperty1
SubItemProperty2
SubItemProperty3
SubNodeItem4
SubNodeItem5
I am able to retrieve the value of any of the SubNode values by using the following syntax:
$val=$XML[$i]->SubNodeItem1;
however, I can not for the life of me figure out how to retrieve the values of SubListItemProperty.
I figured this would be the logical syntax:
$SubItemPropVal=$XML[$i]->SubNodeItemList->SubListItem[$i]->SubItemProperty1;
I have searched other forums and topics related to PHP multi arrays and have not been able to find the proper way to do this.
I am getting a "Trying to get property of non-object" error when I run the code. I'm pretty sure that's the indication that I'm not pointing the node correctly.

Answer 1

My recommendation would be to keep the XML file, which apparently works fine already, and use it.
Transferring its elements into an array does not make much sense to me.
EDIT: The OP does not actually use an array, but a SimpleXML object.
XPath is extremely flexible and powerful in selecting the needed bits from an XML document:
$doc = new DOMDocument();
$doc->loadXML($your_xml);
$xp = new DOMXPath($doc);
// for example
$result = $xp->query("//SubListItem[2]/SubItemProperty1");
if ($result->length)
{
echo $result->item(0)->textContent;
}
SimpleXML would also work:
$xml = simplexml_load_string($result);
// either this ($node will be an array of matches, or FALSE)
$node = $xml->xpath("//SubNodeItemList/SubListItem[1]/SubItemProperty1");
// or this (unless you add a number, [0] will be assumed)
$node = $xml->SubNodeItemList->SubListItem->SubItemProperty1;
Important: Array notation counts from 0, while XPath always counts from 1.
Note that the second option (array notation) will throw run-time errors when the structure of the document is not what your code expects.
With XPath there would simply be no return value, which is easier to handle (no try/catch block necessary, an if ($node) { ... } suffices).
Also note that with SimpleXML, the document element (<MasterNode>) becomes the document. So you would not use $xml->MasterNode->SubNodeItemList, but $xml->SubNodeItemList.