Error with ajax

Error with ajax

Hi. I have a form with some fields ad the field for upload an image. Inside this form there is a table with some rows.  My target is send all form informations to php. 
  1. This is my code:
  3. $(document).ready(function(){
  4.     var array_orari =[];
  5. $("#salva").click(function(){
  6.     
  7.     $('#orari tbody tr').each(function () {
  8.          
  9.           var giorno =  $(this).find(".giorno").html();
  10.           var apertura1 = $(this).find(".ap1").val();
  11.           var chiusura1 = $(this).find(".ch1").val();
  12.           var apertura2 = $(this).find(".ap2").val();
  13.           var chiusura2 = $(this).find(".ch2").val();
  14.           
  15.           array_orari.push({giorno: giorno, apertura1:apertura1, chiusura1:chiusura1, apertura2:apertura2, chiusura2:chiusura2});
  16.           
  17.       });
  18.     
  19.    array_orari = JSON.stringify(array_orari);
  20.       
  21.    
  22.  
  23.     var formData = new FormData($('#data')[0]);
  24.    
  25.     formData.append('array_orari',array_orari);
  26.     
  27.     $.ajax({
  28.         url: 'ristoDao.php',
  29.         type: 'POST',
  30.         dataType:'JSON',
  31.         data: formData,
  32.         success: function (data) {
  33.             alert(data)
  34.         }
  35.        });
  36. });  
  37.     });
  My problem is when try to send the data to php I have an error on ajax. 
Uncaught TypeError: Illegal invocation
I cant't understand the error. Please help me.