(No version information available, might be only in CVS)
DomNode->set_namespace — Sets namespace of a node
Sets the namespace of a node to uri . If there is already a namespace declaration with the same uri in one of the parent nodes of the node, the prefix of this is taken, otherwise it will take the one provided in the optional parameter prefix or generate a random one.
See also domdocument_create_element_ns(), and domnode_add_namespace()