Manual:$wgExtensionInfoMTime

Cache: $wgExtensionInfoMTime
Time to invalidate cache of extensions loaded by the extension registration system.
Introduced in version:	1.25.0 (Gerrit change 166705; git #I7074b65)
Removed in version:	Still in use
Allowed values:	(integer) or false
Default value:	false
Other settings: Alphabetical | By function

Details

When loading extensions through the extension registration system, this can be used to invalidate the cache. A good idea would be to set this to one file, you can just `touch` that one to invalidate the cache.

Example:

$wgExtensionInfoMTime = filemtime( "$IP/LocalSettings.php" );

If set to false, the mtime for each individual JSON file will be checked, which can be slow if a large number of extensions are being loaded.