public function getValues()
    {
        $params = array();
        foreach ($this->expressions as $expr) {
            $values = $expr->getValues();
            foreach ($values as $value) {
                if ($value instanceof \DateTime) {
                    $params[] = $value->format('Y-m-d H:i:s');
                } else {
                    $params[] = $value;
                }
            }
        }

        return $params;
    }