This function returns the real name as specified in the DTD of the specified attr, where attr is the real name or alias of the attribute. Specify element if you want this function to return the real name of an element-specific attribute (element can be a real name or an alias). If element is omitted, this function returns the real name of a global attribute.

The doc argument specifies the identifier of the document tree to query. If omitted or 0, the current document is searched.