library/Rediska/Key/SortedSet.php
public function removeByRank($start, $end)
    {
        return $this->_getRediskaOn()->deleteFromSortedSetByRank($this->getName(), $start, $end);
    }
public function removeByRank($start, $end)
    {
        return $this->_getRediskaOn()->deleteFromSortedSetByRank($this->getName(), $start, $end);
    }
Remove all elements in the sorted set at key with rank between start and end

@param numeric $start Start position
@param numeric $end   End position
@return integer