src/Connection.php
public function open()
    {
        if ($this->_socket !== false) {
            return;
        }
        $connection = ($this->unixSocket ?: $this->hostname . ':' . $this->port) . ', database=' . $this->database;
        \Yii::trace('Opening redis DB connection: ' . $connection, __METHOD__);
        $this->_socket = @stream_socket_client(
            $this->unixSocket ? 'unix://' . $this->unixSocket : 'tcp://' . $this->hostname . ':' . $this->port,
            $errorNumber,
            $errorDescription,
            $this->connectionTimeout ? $this->connectionTimeout : ini_get('default_socket_timeout'),
            $this->socketClientFlags
        );
        if ($this->_socket) {
            if ($this->dataTimeout !== null) {
                stream_set_timeout($this->_socket, $timeout = (int) $this->dataTimeout, (int) (($this->dataTimeout - $timeout) * 1000000));
            }
            if ($this->password !== null) {
                $this->executeCommand('AUTH', [$this->password]);
            }
            if ($this->database !== null) {
                $this->executeCommand('SELECT', [$this->database]);
            }
            $this->initConnection();
        } else {
            \Yii::error("Failed to open redis DB connection ($connection): $errorNumber - $errorDescription", __CLASS__);
            $message = YII_DEBUG ? "Failed to open redis DB connection ($connection): $errorNumber - $errorDescription" : 'Failed to open DB connection.';
            throw new Exception($message, $errorDescription, $errorNumber);
        }
    }
public function open()
    {
        if ($this->_socket !== false) {
            return;
        }
        $connection = ($this->unixSocket ?: $this->hostname . ':' . $this->port) . ', database=' . $this->database;
        \Yii::trace('Opening redis DB connection: ' . $connection, __METHOD__);
        $this->_socket = @stream_socket_client(
            $this->unixSocket ? 'unix://' . $this->unixSocket : 'tcp://' . $this->hostname . ':' . $this->port,
            $errorNumber,
            $errorDescription,
            $this->connectionTimeout ? $this->connectionTimeout : ini_get('default_socket_timeout'),
            $this->socketClientFlags
        );
        if ($this->_socket) {
            if ($this->dataTimeout !== null) {
                stream_set_timeout($this->_socket, $timeout = (int) $this->dataTimeout, (int) (($this->dataTimeout - $timeout) * 1000000));
            }
            if ($this->password !== null) {
                $this->executeCommand('AUTH', [$this->password]);
            }
            if ($this->database !== null) {
                $this->executeCommand('SELECT', [$this->database]);
            }
            $this->initConnection();
        } else {
            \Yii::error("Failed to open redis DB connection ($connection): $errorNumber - $errorDescription", __CLASS__);
            $message = YII_DEBUG ? "Failed to open redis DB connection ($connection): $errorNumber - $errorDescription" : 'Failed to open DB connection.';
            throw new Exception($message, $errorDescription, $errorNumber);
        }
    }
Establishes a DB connection.
It does nothing if a DB connection has already been established.
@throws Exception if connection fails