[imedia]

var type=1;
 $.ajax({
          type: 'POST',
		  dataType:'json',
          url: '/functions_ajax/save_model',
		  data:{type:type},
          success: function(data){
		alert(data)
		},
          error:  function(xhr, str){
                alert('Возникла ошибка: ' + xhr.responseCode);
            }
        });

public function save_model(){
	header('Content-Type: application/json');
	$jnd='ответ';
	if(isset($jnd)){
	echo json_encode($jnd);
	}
	else{
	echo json_encode(null);
	}
	}