当它到达php页面时，是ajax @post为空

Question

I have the following code where I attempt to post values to a php file using ajax/json. The php file throws warnings saying: Undefined index: companyid, Undefined index: companyname, Undefined index: calendar_eventStart, Undefined index: calendar_eventEnd. I realize that the variables posted using ajax are empty when they are picked up on the server side, but I don't see what I'm doing wrong. Here is my code:

Console log:

Data: {"companyid":1,"companyname":"Fifteen AS","calendar_eventStart":"2018-06-06T22:00:00.000Z","calendar_eventEnd":"2018-06-06T22:00:00.000Z"}

jQuery:

var formData = {
                    companyid,
                    companyname,
                    calendar_eventStart,
                    calendar_eventEnd
                };
                formData = (JSON.stringify(formData));
                console.log('Data: ' + formData);                   
                $.ajax({
                url: "create_calendar_event.php",
                type: "post",
                dataType: "json",   
                data:{data: formData},                   
                success: function(response) {
                alert(response);                
                }               
                });

PHP:

var_dump($_POST['companyid']);
var_dump($_POST['companyname']);
var_dump($_POST['calendar_eventStart']);
var_dump($_POST['calendar_eventEnd']);
$event_status = 'Success';
echo json_encode($event_status,JSON_UNESCAPED_UNICODE|JSON_UNESCAPED_SLASHES);