“Could not connect to MySQL.” Error on a Joomla Website

Yesterday (Friday) we explained how a full disk brought the Joomla website of a client of ours completely down. We also mentioned that we upgraded the VPS plan of that client to a more generous plan in terms of disk drive and memory – what we didn’t mention, however, was that the VPS upgrade did not go smoothly, because when the upgrade was done, we saw the following error on the homepage of the website:

Error displaying the error page: Application Instantiation Error: Could not connect to MySQL.

Now, probably most of those who have an intermediate knowledge of Joomla know that the above error is caused by one of the following:

  • The database username and/or password and/or database name and/or database host is/are wrong.

  • The database user does not have full read/write access to the database.

  • The database server is not running.

  • The mysqli PHP module is not installed.

We were confident that the error was not caused by any of the above, nevertheless, we decided to create a small PHP file that will test the connection to the database just to be sure. So, we created a file called check-mysql-connection.php which contained the below code:

<?php
$dbConnection = new mysqli("localhost", "[db-username]", "[db-password]", "[db-database-name]");
if ($dbConnection ->connect_errno !== FALSE)
	echo $dbConnection ->connect_error.' (Error Number: '.$dbConnection ->connect_errno.')';

?>

Running the above file generated the following error:

Warning: mysqli::mysqli(): (HY000/2002): No such file or directory in /home/[cpanel-user]/public_html/check-mysql-connection.php on line 2
No such file or directory (Error Number: 2002)

Hmmm! So it was something with mysqli. We immediately assumed that it wasn’t installed on the new VPS instance, so we logged in to WHM, went to EasyApache 3, and then checked the ** DEFAULT ** (selected) profile. We noticed 2 things:

  • The mysqli module was installed.

  • The VPS instance was running an EOL (End Of Life) version of PHP, which was version 5.4.45.

So we switched, on the PHP Version page (in EasyApache), to PHP 5.5.37. We then clicked on Next Step, and then we clicked on Save and Build. We followed the instructions and then tested the website, and this time it worked!

But why didn’t the mysqli PHP module work with PHP 5.4.45?

We suspect that was because the installed mysqli module wasn’t compatible with that version of PHP. Upgrading to PHP 5.5.37 ensured that everything was compatible with that particular version of PHP.

So, the next time you see that Could not connect to MySQL error on your Joomla website, make sure (after verifying the obvious: username, password, host, permissions, etc…) that the problem is not with your version of PHP. If you need help finding and fixing the problem, then that’s what we’re here for. Just contact us and we’ll solve the problem for you quickly, professionally, and for a very small fee!

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