SimpleXMLElement: asXML() "on a non-object" that really is an object - php

Question

I am parsing a SVG file using SimpleXMLElement in PHP. The SVG file is carefully constructed in Adobe Illustrator follow a layer format that I am attempted to dissect.
Consider this code:
// Create an XML object out of the SVG
$svg = new SimpleXMLElement('floorplan.svg', null, true);
// Register the SVG namespace
$svg->registerXPathNamespace('svg', 'http://www.w3.org/2000/svg');
// Get the normal floorplan layer
$normal = $svg->xpath('svg:g[#id="Normal"]');
// If the normal layer has content, continue
if(count($normal) > 0) {
// If there are floors, continue
if(count($normal[0]->g > 0)) {
// Loop through each floor
foreach($normal[0]->g as $floor) {
// Declare the namespace for the floor
$floor->registerXPathNamespace('svg', 'http://www.w3.org/2000/svg');
// Select the base floorplan
$floorsvg = $floor->xpath('svg:g[#id="Base"]')[0];
var_dump($floorsvg);
echo $floorsvg->asXML(); // THIS CAUSES THE ERROR
}
}
}
When I do a var_dump on $floorsvg, it is declaring it is a SimpleXMLElement object:
object(SimpleXMLElement)[9]
public '#attributes' =>
array (size=1)
'id' => string 'Base' (length=4)
public 'g' =>
array (size=859)
0 => ...
However, when I run asXML() on the object, I am presented with the following PHP error:
PHP Fatal error: Call to a member function asXML() on a non-object
I'm uncertain why asXML() is failing, considering it is an object. Can anyone shed any light on why this problem is occurring and what I might try to remedy it?
EDIT: Adding an echo $normal->asXML(); up above results in the same error. It seems like xpath is causing the object to become malformed somehow.
EDIT 2: The SVG file being parsed can be seen here: http://pastebin.com/zK1yRFA7

Answer 1

There are a few issues. Your code assumes that:
$floor->xpath('svg:g[#id="Base"]')
Will return an array with at least 1 element. The <g id="Second_Floor"> element does not contain any child elements that will be matched by that XPath expression, so trying to access element 0 of an empty array will give you the error you are seeing.
Adding a simple guard expression:
// Select the base floorplan
$floorsvg = $floor->xpath('svg:g[#id="Base"]')
if (count($floorsvg) > 0) {
echo $floorsvg[0]->asXML();
}
Will resolve that. Secondly, you have some misplaced parentheses in this line:
if(count($normal[0]->g > 0)) {
It should be:
if(count($normal[0]->g) > 0) {
Appears to be just a simple typo and doesn't appear to affect the outcome of this particular script one way or another.