Software Development:
Individual Programming

Symptom

When you run a script or install a software among other errors you might see a message „call to undefined function mysql_connect()“. The script stops, the software cannot be installed. This is the case for Piwik installations from the application repository, for example.

Cause

In the past, PHP had two MySQL extensions: MySQL and MySQLi. The “I” in “MySQLi” stands for “improved”. MySQLi is the better, faster and more versatile PP extension to communication with MySQL databases. In PHP 7.0 the old MySQL extensions was completely removed. Now only the MySQLi extension is available. The PHP function “mysql_connect()” is unavailable, because your web space is using a PP version newer than 5.6. Many old scripts are still using the outdated MySQL extension. For that reason they will not work with newer PHP versions.

Solution

Depending on the situation there are different approaches to resolve the issue:

a) You can downgrade the PHP version in your web space control panel to version 5.6. To downgrade, click on the “PHP settings” icon and choose PHP version 5.6. It does not matter whether you select the FastCGI or FPM interface. FPM is recommended, because it is faster, and it is today’s default. Unfortunately it is less stable, too. After the downgrade it can take up to 15 minutes before the web server applies the changes.

b) When you are using a third-party software that still requires the outdated MySQL extension, ask the manufacturer, if they offer a newer version. Many manufacturers have updated their software so that it works with new PHP versions.

c) When you have developed your script on your own, we recommend to update all MySQL functions with the corresponding MySQL functions. This will ensure that your script will continue to work with future web hosting environments.

Newer PHP versions have big advantages over the old PHP 5.6 in terms of resource management and speed. Whereever possible you should prefer to update your scripts so that they work with new PHP versions instead of downgrading PHP to an old version.

Overview of frequently asked questions