library/Rediska/Serializer.php
public function serialize($value)
    {
        if (is_numeric($value) || is_string($value)) {
            return (string)$value;
        } else {
            return $this->_adapter->serialize($value);
        }
    }
public function serialize($value)
    {
        if (is_numeric($value) || is_string($value)) {
            return (string)$value;
        } else {
            return $this->_adapter->serialize($value);
        }
    }
Serialize value

@param mixed $value Value for serialize
@return string