db.php

<?php

// $this->qb() returns an instance of \Doctrine\DBAL\Query\QueryBuilder from \Doctrine\DBAL\Connection

public function insertNewRank(
        string $name,
        int $flags
    ): int {
        $qb = $this->qb();
        $qb->insert(self::TABLE)
            ->values([
                'name' => $qb->createNamedParameter($name),
                'flags' => $qb->createNamedParameter($flags)
            ])->executeStatement();
        return (int) $this->connection->lastInsertId();
}
//Params here are passed straight from $_POST
    public function insertUser(
        string $firstName,
        string $lastName,
        string $email,
        string $password
    ): ?int {
        try {
            $qb = $this->qb();
            $qb->insert(self::TABLE)
                ->values([
                    'firstName' => $qb->createNamedParameter($firstName),
                    'lastName' => $qb->createNamedParameter($lastName),
                    'email' => $qb->createNamedParameter($email),
                    'password' => $qb->createNamedParameter($password),
                    'created_ip' => $qb->createNamedParameter(ip2long($_SERVER['REMOTE_ADDR']))
                ])->executeStatement();
            return (int) $this->connection->lastInsertId();
        } catch (Exception $e) {
            return null;
        }
    }