library/Rediska/Key.php
public function substring($start, $end = -1)
    {
        return $this->_getRediskaOn()->substring($this->getName(), $start, $end);
    }
public function substring($start, $end = -1)
    {
        return $this->_getRediskaOn()->substring($this->getName(), $start, $end);
    }
Get range

@deprecated
@param integer           $start Start
@param integer[optional] $end   End. If end is omitted, the substring starting from $start until the end of the string will be returned. For default end of string
@return mixin