Eg, if you pass it pageID = 5 and your delta is 2 it will return you 3 and 7. PageID of 6 would give you 4 and 8
NB: The behaviour of this function could be misleading: it was left only for compatibility with PEAR::Pager. It could raise some confusion when pageID is within delta positions from an extreme: in fact this method returns also the extremes, while $this->_getPageLinks leaves them out. Pager_Sliding works this way: if pageID is NOT an extreme, show first and last page within brackets:  << 5 | _6_ | 7 >>  So when dealing with pageID within delta positions from an extreme, this method would return the extreme as well, while $this->_getPageLinks would return (for instance) 2 | _3_ | 4 | 5 even if pageID is 3 and delta is 2. Consider this method deprecated and/or subject to changes.