Manual:$wgScriptExtension

Details
Extension to append to script names by default.

This can either be   or  .

Some hosting providers used PHP 4 for *.php files, and PHP 5 for *.php5.

This variable was provided to support those providers.

In MediaWiki 1.27, this setting has been removed. In order to preserve support for '.php5' entry points, you can set up URL rewriting from .php5 files to .php files.