Is it possible to set the PHP version value, say 4.0+ and have PHPStorm highlight functions that wouldn't work with the oldest version? For example, for PHP4 this should highlight
so, you mean to highlight all pieces of code that will not work in the version you are writing it, right? That can be done in:
Preferences -> Languages & Frameworks > PHP
then select your version, for example, 7.0
This is very useful when your local is in 7.0, for example, but production is in 5.5. That way phpstorm will warning you which parts will not work in production.