MysqliConnection::connectInternal

protected function connectInternal()
{
	if ($this->isConnected)
	{
		return;
	}

	$host = $this->host;
	$port = 0;
	if (($pos = strpos($host, ":")) !== false)
	{
		$port = intval(substr($host, $pos + 1));
		$host = substr($host, 0, $pos);
	}
	if (($this->options & self::PERSISTENT) != 0)
	{
		$host = "p:".$host;
	}

	$connection = mysqli_init();
	if (!$connection)
	{
		throw new ConnectionException('Mysql init failed');
	}

	if (!empty($this->initCommand))
	{
		if (!$connection->options(MYSQLI_INIT_COMMAND, $this->initCommand))
		{
			throw new ConnectionException('Setting mysql init command failed');
		}
	}

	if ($port > 0)
	{
		$success = $connection->real_connect($host, $this->login, $this->password, $this->database, $port);
	}
	else
	{
		$success = $connection->real_connect($host, $this->login, $this->password, $this->database);
	}

	if (!$success)
	{
		throw new ConnectionException(
			'Mysql connect error ['.$this->host.']',
			sprintf('(%s) %s', $connection->connect_errno, $connection->connect_error)
		);
	}

	$this->resource = $connection;
	$this->isConnected = true;

	if (isset($this->configuration['charset']))
	{
		$connection->set_charset($this->configuration['charset']);
	}

	// nosql memcached driver
	if (isset($this->configuration['memcache']))
	{
		if (function_exists('mysqlnd_memcache_set'))
		{
			$memcached = BitrixMainApplication::getInstance()->getConnectionPool()->getConnection($this->configuration['memcache']);
			mysqlnd_memcache_set($this->resource, $memcached->getResource());
		}
	}

	$this->afterConnected();
}