As a junior I am glad I happened to start working with PHP on version 7. I had some peeks at our legacy PHP5 stuff (all killed now thankfully) and it looked very different. I am sure it would suck to work with.

php7 was such a great time period for PHP, honestly lots of great experimental projects around that time too (HHVM before that, etc).

PHP 8 is good too. Lots of syntactic sugar to make your life so, so much easier.