(no version information, might be only in CVS)
DomNode->previous_sibling -- 
     Returns the previous sibling of node
    
Description
object 
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().