array Pager::getPageRangeByPageId ( 
      integer $pageid
        = null
      
     )
Given a PageId, it returns the limits of the range of pages displayed. While getOffsetByPageId() returns the offset of the data within the current page, this method returns the offsets of the page numbers interval.
      E.g., in "Jumping" mode, if you have pageId=3 and
      delta=10, it will return (1, 10).
      pageID=8 would give you (1, 10) as well, because
      1 <= 8 <= 10.
      pageID=11 would give you (11, 20).
     
      In "Sliding" mode, if you have pageId=5 and
      delta=2, it will return (3, 7).
      pageID of 9 would give you (4, 8).
     
      if the method is called
      without parameter, pageID is set to currentPage number
     
        integer $pageid - PageID to get offsets for
       
return array with first and last offsets