Would you please give us a link where it doesn't work? Our server-side DataTables example works correctly with filter (please be patient as searching 3 million rows takes a few seconds):

https://www.koolreport.com/examples/reports/datagrid/server_processing/

Also, if your data source is large with, says, millions of rows, it's advisable to set `searchOnEnter" = true so that any change in filter doesn't trigger a search:

DataTables::create(array(
    ...
    "serverSide"=>true,
    "method"=>'post', //default = 'get'
    "searchOnEnter" => true,
));