Manual:$wgScriptExtension

Server URLs and file paths: $wgScriptExtension
Extension to append to script names by default.
Introduced in version:	1.11.0
Deprecated in version:	1.25.0 (Gerrit change 244199; git #7628a11d)
Removed in version:	1.31.0 (Gerrit change 411484; git #de6dab71)
Allowed values:	(string)
Default value:	'.php'
Other settings: Alphabetical | By function

Details

Extension to append to script names by default. This can either be ".php" or ".php5".

Some hosting providers used PHP 4 for *.php files, and PHP 5 for *.php5. This variable was provided to support those providers.

Now that this setting has been removed you can set up URL rewriting from ".php5" files to ".php" files to continue supporting ".php5" entry points.