If your project is stuck on PHP 7.4 and you truly need PhpStorm 2019 because newer versions break your custom plugins, consider this legal workflow:
JetBrains provides free individual educational licenses for students and teachers. If you are verified through GitHub Education phpstorm 2019 license github
: Students can get a free annual subscription to all JetBrains IDEs. Apply via the GitHub Education portal. Verify your student status with a school email or ID. Renewals are available as long as you remain a student. If your project is stuck on PHP 7