PHP 8.3 is the active development branch of PHP versions. It's the current target for new RFCs, and is scheduled to be released towards the end of 2023.
PHP 8.2 is the latest PHP version which brings readonly classes, DNF types, null, false, and true types, sensitive parameter redaction support, a new random extension, and several new features along with a few deprecations.
PHP 8.1, released in 2021, brings major new features such as Enums, Fibers, never return type, Intersection Types, readonly properties, and more, while ironing out some of its undesired legacy features by deprecating them.
PHP 8.0, on the 25th year of PHP history, brings several important features such as Union Types, JIT, Constructor Property Promotion, Match Syntax, Named Parameters, and several more performance, syntax, and quality-of-life improvements.
PHP 7.4, the final release in the PHP 7.x series. PHP 7.4 brings typed properties, underscore numeric separator, and other minor improvements to PHP.