the issue is that some Apache servers will treat files with .php anywhere in the file as php.
So the lighter.php.js file is being processed by the php engine instead of being treated as a js file.
the work around is to set the handler mapping in Apache to only process a file as php if it ends in .php.
the people who wrote the lighter.php.js code have the following FAQ:
you may need o contact your host to make the change to the handler mapping.