This method can be used to remove a namespace declaration from an element, even though the declaration is not considered an attribute by the DOM. The prefix will be removed from any element or attribute using it.
<?php
$dom = DOMDocument::loadXML('<foo:root xmlns:foo="http:bar"/>');
$element = $dom->childNodes->item(0);
// prints '0':
echo (int) $element->hasAttributeNS('http:bar', 'foo');
$element->removeAttributeNS('http:bar', 'foo');
/* prints '<?xml version="1.0"?> <root/>': */
print htmlentities($dom->saveXML());
?>
DOMElement->removeAttributeNode()