I am trying to upload file using ajax in codeigniter framework. My code work without using ajax but when i use ajax i got error message 'Undefined index: picture'in if($_FILES['picture']['name']).
Please check this code
View :
<form enctype="multipart/form-data" method="post">
   <div class="form-group">
      <label for="int">Picture</label>
      <input type="file" id="picture" name="picture" class="dropify" data-height="300" />
   </div>
</form>
AJAX :
var picture=new FormData( $("#picture")[0] );
var url = "<?php echo site_url('Workscontroller/create_action'); ?>";  
            $.ajax({
              url:url,
              data: {"title":title,"caption":caption,"description":description,"kategori":kategori,"picture":picture},
              dataType:"JSON",
              type:"POST",
              mimeType: "multipart/form-data",
              contentType: false,  
              cache: false,  
              processData:false,  
              success:function(data){  
               swal("Berhasil ditambahkan!", "Anda berhasil menambahkan porto folio.", "success")
               window.location.replace(data.url);
           }  
       }); 
Controller :
$this->load->library('upload');
   $this->_rules();
    $nmfile = "file_".time(); //nama file saya beri nama langsung dan diikuti fungsi time
    $config['upload_path'] = './works/'; //path folder
    $config['allowed_types'] = 'gif|jpg|png|jpeg|bmp'; //type yang dapat diakses bisa anda sesuaikan
    $config['max_size'] = '2048'; //maksimum besar file 2M
    $config['max_width']  = '2000'; //lebar maksimum 1288 px
    $config['max_height']  = '2000'; //tinggi maksimu 768 px
    $config['file_name'] = $nmfile; //nama yang terupload nantinya
    $this->upload->initialize($config);
    if($_FILES['picture']['name'])
    {
        if ($this->upload->do_upload('picture'))
        {
           $gbr = $this->upload->data();
           $data = array(
              'title' => $this->input->post('title',TRUE),
              'caption' => $this->input->post('caption',TRUE),
              'description' => $this->input->post('description',TRUE),
              'picture' => $gbr['file_name'],
              'kategori' => $this->input->post('kategori',TRUE),
              );
           $this->WorksModel->insert($data);
       }
   }
   else{
   }
 
     
    