Server side filtering error

Hello guys,

I've got a problem using DataTabvle 1.9. I've created the server side script in php with all the filter operations,and the ajax interaction with the table. When I first load the page the Table correcty populate itself with all the data.
When I insert a search string the table show the "processing" message but nothing happens. I've checked server side and the query is correct, also the json data in output seems corrected filtered.

Someone can give me some advice?

Thank you very much

Alessandro