PhpStorm open external file in project with inspection and highlighting

Question

This might be a minor issue, but I often have to fight with it.

I have many files without extension outside my project folder and I want to open these files as PHP files. Meaning the indentation, syntax-highlighting and completions is correct.
I haven't yet found a setting where I can force a file without extension to be treated as PHP file.

Anybody able to help?

Answer 1

Adding an empty extension for PHP files in Settings | File Types may help, but it may be dangerous as all the files without extension will be treated as PHP files.