<?php

$xml = <<< XML
<Item>
    <Image
        source="http://upload.wikimedia.org/Vinberg.svg.png"
	width="50"
	height="41"/>
</Item>
XML;

$item = new SimpleXMLElement($xml);
echo $item->Image['source'];

foreach ($item->Image->attributes() as $attributeName => $attributeValue) {
    printf("\n%s => %s", $attributeName, $attributeValue);
}

http://upload.wikimedia.org/Vinberg.svg.png
source => http://upload.wikimedia.org/Vinberg.svg.png
width => 50
height => 41