XMLReader::getAttribute

Or use XMLReader::ELEMENT and XMLReader::END_ELEMENT rather than the numbers 1 and 15.

might be obvious, but not to everyone ;-) ... when reading attributes from a node that has sub-nodes (and creating an output from this node), the output will be issued twice, once on the <ELEMENT> tag and once on the end tag </ELEMENT>. To avoid this, you can test on which part of the node you are using the property nodeType. 
It'll be 1 for the element, 15 for the end element.

To get all attributes and their names, use something like this:
<?php
function getAttributes($reader)
{
 $attributes = [];
 for ($i = 0; $i < $reader->attributeCount; $i++) {
 $reader->moveToAttributeNo($i);
 $attributes[$reader->name] = $reader->value;
 }
 return $attributes;
}
?>