Think/Db/Driver.php
public function connect($config = '', $linkNum = 0, $autoConnection = false)
    {
        if (!isset($this->linkID[$linkNum])) {
            if (empty($config)) {
                $config = $this->config;
            }
            try {
                if (empty($config['dsn'])) {
                    $config['dsn'] = $this->parseDsn($config);
                }
                $this->linkID[$linkNum] = new PDO(
                    $config['dsn'],
                    $config['username'],
                    $config['password'],
                    $this->options
                );
            } catch (PDOException $e) {
                if ($autoConnection) {
                    trace($e->getMessage(), '', 'ERR');

                    return $this->connect($autoConnection, $linkNum);
                } elseif ($config['debug']) {
                    throw new BaseException($e->getMessage());
                }
            }
        }

        return $this->linkID[$linkNum];
    }
public function connect($config = '', $linkNum = 0, $autoConnection = false)
    {
        if (!isset($this->linkID[$linkNum])) {
            if (empty($config)) {
                $config = $this->config;
            }
            try {
                if (empty($config['dsn'])) {
                    $config['dsn'] = $this->parseDsn($config);
                }
                $this->linkID[$linkNum] = new PDO(
                    $config['dsn'],
                    $config['username'],
                    $config['password'],
                    $this->options
                );
            } catch (PDOException $e) {
                if ($autoConnection) {
                    trace($e->getMessage(), '', 'ERR');

                    return $this->connect($autoConnection, $linkNum);
                } elseif ($config['debug']) {
                    throw new BaseException($e->getMessage());
                }
            }
        }

        return $this->linkID[$linkNum];
    }
连接数据库方法


@param string $config
@param int $linkNum
@param bool $autoConnection
@return mixed|PDO
@throws BaseException