src/IdentityModel.php
public function existLogin(string $login): int
    {
        return (int) $this->connection->select(self::COLUMN_ID)
            ->from($this->tableIdentity)
            ->where(['login' => $login])
            ->fetchSingle();
    }
public function existLogin(string $login): int
    {
        return (int) $this->connection->select(self::COLUMN_ID)
            ->from($this->tableIdentity)
            ->where(['login' => $login])
            ->fetchSingle();
    }
Exist login.

@param string $login
@return int