(no version information, might be only in CVS)
DomNode->previous_sibling -- 
   Returns the previous sibling of node
  
Description
domelement 
DomNode->previous_sibling ( void  )
   This function returns the previous sibling of the current node. If there 
   is no previous sibling it returns FALSE (< 4.3) or NULL (>= 4.3). You 
   can use this function to iterate over all children of a node as shown in 
   the example.
  
   See also domnode_next_sibling().