Manual:$wgCachedMessageArrays

Message Cache: $wgCachedMessageArrays
Directory for compiled constant message array databases.
Introduced in version:1.6.0 (r12812)
Removed in version:1.8.0
Allowed values:(path string) or false
Default value:false

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Directory for compiled constant message array databases.

  Warning: Turning anything on will just break things, aaaaaah!!!!