Comment 4 for bug 1247715

To add some additional info about the link that Robert just posted, the issue is that, if you specifically supply a $CFG->dbport value, then Mahara appends that to the end of your $CFG->dbhost value before sending it to mysqli_real_connect(), like "localhost:3306". The problem is that mysqli doesn't support that. Instead, we need to supply the port number as a separate argument (the fifth) to mysqli_real_connect(). Implementation-wise, in order to do that in ADODB, we need to manually set the "$this->port" for the ADODB_mysqli object.

The workaround, is that if you're using port 3306 (which is the default for MySQL), simply remove the $cfg->dbport line from your config.php file.

If you are not using port 3306, then you'll need to patch the software to fix it.