(PHP 5 >= 5.2.0, PHP 7)
Creates a prefix/ns context for the next XPath query
public bool SimpleXMLElement::registerXPathNamespace ( string $prefix, string $ns )
Creates a prefix/ns context for the next XPath query. In particular, this is helpful if the provider of the given XML document alters the namespace prefixes. registerXPathNamespace will create a prefix for the associated namespace, allowing one to access nodes i