If you are working everyday with Drupal module development you know how frustrating can be that each time you open a module file its show in plaintext instead of in PHP format. Well there is a easy solution, open up your Notepad++ and go to Settings -> Style Configurator.

Depending on which language color syntax you want for the file extension, under Language, select the language.

Select php under Language.

In User ext., copy/paste this string: module inc install

After that, Save & Close.