1. Create a new idea plugin project in Idea from this repository.
2. Add your java home as a java sdk. (File/Project Structure/Sdks)
3. Add your phpstorm directory as an intellij plugin sdk. (File/Project Structure/Sdks)
4. Use these VM options in a plugin run configuration:

-Didea.platform.prefix=PhpStorm -Xms128m -Xmx800m -XX:MaxPermSize=350m -XX:ReservedCodeCacheSize=64m -XX:+UseCompressedOops