The very latest stable mainaned PHP versions available are:
8.1.7, 8.0.20, 7.4.30
If you are running a supported major/minor release (8.1, 8.0, 7.4) but the final part of the version number is lower than one of the versions listed above then your web server is not running the latest patch release.
This is something you should aim to resolve as soon as possible as it's highly likely that many of the changes in the latest patch releases you have missed are fixes for security vulnerabilities.
See our full list of PHP version expiry dates here.
If you know exactly which revision (down to the patch version) your web server is using then read this guide on how to get PHP updated.
If you need a guide on how to find out what version you are running just click here.