Change record status: 
Project: 
Introduced in branch: 
8.0.x
Introduced in version: 
8.0.0-beta7
Description: 

In Drupal we have more or less 6 non-standard extensions to represent PHP files. Now all these files end with .php extension.

Old → New
foo.module → foo.module.php
foo.install → foo.install.php
foo.inc → foo.inc.php
bar.theme → bar.theme.php
baz.profile → baz.profile.php
qux.engine → qux.engine.php

This command line script will help in renaming files within contrib or custom modules and themes.

for f in $(find . -name "*.module" -o -name "*.profile" -o -name "*.theme" -o -name "*.install" -o -name "*.inc" -o -name "*.engine"); do mv $f ${f}.php; done

Renaming through git (use git mv instead of mv):

for f in $(find . -name "*.module" -o -name "*.profile" -o -name "*.theme" -o -name "*.install" -o -name "*.inc" -o -name "*.engine"); do git mv $f ${f}.php; done
Impacts: 
Site builders, administrators, editors
Module developers
Themers