id function finds nodes matching the given ids and returns a node-set containing the identified nodes.
id( expression )
expressionis a node-set, then the string value of each node in the node-set is treated as an individual id. The returned node set is the nodes corresponding to those ids.
expressionis a string, or anything other than a node-set, then
expressionis treated as a space-separated list of ids. The returned node set is the nodes corresponding to those ids.
A node-set containing the node or nodes identified by the given id or ids.
- The DTD of the XML document determines what attribute is an ID. See XPath 1.0 5.2.1