library/Rediska/Key/Hash.php
public function increment($field, $amount = 1)
    {
        $result = $this->_getRediskaOn()->incrementInHash($this->getName(), $field, $amount);

        if (!is_null($this->getExpire()) && $result) {
            $this->expire($this->getExpire(), $this->isExpireTimestamp());
        }

        return $result;
    }
public function increment($field, $amount = 1)
    {
        $result = $this->_getRediskaOn()->incrementInHash($this->getName(), $field, $amount);

        if (!is_null($this->getExpire()) && $result) {
            $this->expire($this->getExpire(), $this->isExpireTimestamp());
        }

        return $result;
    }
Increment field value in hash

@param mixed  $field            Field
@param number $amount[optional] Increment amount. Default: 1
@return integer