This function replaces the child oldnode
with the passed new node. If the new node is already a child it
will not be added a second time. If the replacement succeeds the
old node is returned.
newnodeThe new node. It must be a member of the target document, i.e. created by one of the DOMDocument->createXXX() methods or imported in the document by DOMDocument->importNode().
oldnodeThe old node.
Raised if this node is readonly or if the previous parent of the node being inserted is readonly.
Raised if this node is of a type that does not allow children of the
type of the newnode node, or if the node to
put in is one of this node's ancestors or this node itself.
Raised if newnode was created from a different
document than the one that created this node.
Raised if oldnode is not a child of this node.