PHP versions follow the official PHP release cycle. Once a version reaches the end of its security support window it stops receiving updates here as well, but existing packages stay available in the repository so current installations keep working.
An operating system is supported for as long as it is within its vendor's full support window - for example, RHEL 8 left full support on 31 May 2024. Packages for an operating system past that point may still be updated for longer at my discretion, but there is no guarantee.
Support at GitHub