Do I need to keep older versions of MySQL and PHP installed on my hosting servers if I've already installed the latest versions, and which specific older versions would you suggest I keep?
Thank you.

In general, it's recommended to use only the supported versions of PHP which currently include 7.4, 8.0, and 8.1. However, some enterprise distros such as RHEL and its derivatives like CentOS, Alma, Rocky, and Oracle provide long-term support for their PHP versions (usually around 8 years). For instance, CentOS 7 uses PHP 5.4.16, which is fully supported with 2 more years until its EOL.
It's important to note that if you're using a control panel like cPanel, they may have their own set of supported PHP versions.

I've noticed that many people still use PHP 5 or older versions on their outdated websites.
While hosting these clients who are too lazy to update their code could be a positive thing, it's unlikely that they will switch to newer versions of PHP if they are already resistant to change.

InterServer offers a shared hosting Standard plan that includes unlimited storage, sites, MySQL databases, and traffic. PHP versions 5.5 and 5.6, as well as 7.0 and higher, are supported, and the service comes with tools for optimizing PHP sites. The cPanel control panel allows users to switch between PHP versions and customize settings easily. Additionally, the service is available in multiple languages, and there is a fixed price guarantee for shared hosting plans.

Introducing their pro hosting solution, Schneider Host provides hosting for websites that require more system resources than regular hosting, offering faster speeds and greater stability. Pro hosting allows users to use up to 17% of the CPU and RAM resources, with weekly backups and extended technical support. This is a cheaper alternative to a VPS, with the only disadvantage being the lack of root access. For trusted customers, they offer the PRO-mini tariff, which allows users to get all the benefits of PRO hosting at a lower fee, with slightly reduced resource allowance and regular technical support.

The necessity of keeping older versions of MySQL and PHP depends on the compatibility requirements of your applications and websites. If the latest versions of MySQL and PHP are fully compatible with your code, you may not need to keep the older versions.

However, it's generally advised to keep a few previous versions for a period of time to ensure a smooth transition in case any compatibility issues arise. This allows you to roll back to a working version if needed.

As for specific versions, it's important to consider your application's dependencies, including frameworks and plugins. Identify the requirements of these dependencies and check their compatibility with different versions of MySQL and PHP. Based on this information, determine which specific older versions to retain.

Ultimately, the decision depends on your specific use case and the needs of your applications.