Warning Errors in Log

To use Autocomplete in my forms I followed the answer here: http://stackoverflow.com/questions/32464016/cakephp-3-0-autocomplete-jquery-ui and it works properly EXCEPT I get errors logged every time the autocomplete is used: 2016-11-09 16:24:44 Warning: Warning (2): Cannot modify header information - headers already sent by (output started at /apps/water-assets/src/Controller/RealEstateRequestsControll‌​er.php:152) in [/apps/water-assets/vendor/cakephp/cakephp/src/Http/Response‌​Emitter.php, line 170] which is the echo json_encode($resultArr); line. How can I solve this error?

Hello @naidim. I have usually got that kind of warnings when there is any notice or warning as part of the response.