In this example I will show you how you can set OpenCart’sfile extension to read as PHP when opening in Atom Editor.
Open yourfile. Underneath add:
customFileTypes: 'text.html.php': [ 'tpl' ]
is the “source” and the tpl is the file extension. Now when you open a file it will read as a PHP file by default.
If you want any other custom file types you can follow this format, full directions found on flight manual.