PHP development is anything but "over". For as long as platforms such as WordPress, Joomla, Drupal, Flarum etc continue to use it, the language will only improve. Version 8 is scheduled for release soon.
Let's not forget that PHP is primarily a backend language designed to talk to the server on behalf of the client app which can be running JS etc. Ajax calls are used to push and pull data requests, and it's still an extremely powerful codebase that will only get faster with the release of 8.