Manual:$wgUseOldSearchUI

Miscellaneous settings: $wgUseOldSearchUI
Whether to use the "old" search UI
Introduced in version:1.14.0 (r43595)
Removed in version:1.16.0 (r54030)
Allowed values:(boolean)
Default value:true

Details edit

Whether to use the "old" search user interface.

The new search UI is always used as of 1.16.0.