如何从jquery ' formData '中提取值以插入Mysql

我的代码是关于通过$.ajax提交multipart form，这是成功地做到了&在submit.php中的json_encode上，它给了我这个:

{"success":"Image was submitted","formData":{"fb_link":"https:'/'/www.google.mv'/",
"show_fb":"1",
"filenames":[".'/uploads'/homepage-header-social-icons'/27.jpg"]}}

有人能解释我，在submit.php，我怎么能从formData提取值，存储在mysql表?我试过了，很多事情包括:

 $fb_link = formData['fb_link'];
 $show_fb = formData['show_fb'];

和

$arr = json_encode($data);
$fb_link=$arr['fb_link'];

和

$fb_link = REQUEST['fb_link'];
 $show_fb = REQUEST['show_fb'];

但是，似乎没有工作?

更新:父页面上的JS代码为:

      $(function()
      {
      // Variable to store your files
      var files;
      // Add events
      $('input[type=file]').on('change', prepareUpload);
      $('form#upload_form').on('submit', uploadFiles);
      // Grab the files and set them to our variable
      function prepareUpload(event)
      {
      files = event.target.files;
      }
      // Catch the form submit and upload the files
      function uploadFiles(event)
      {
      event.stopPropagation(); // Stop stuff happening
      event.preventDefault(); // Totally stop stuff happening
      // START A LOADING SPINNER HERE
      // Create a formdata object and add the files
      var data = new FormData();
      $.each(files, function(key, value)
      {
      data.append(key, value);
      });
      //var data = new FormData($(this)[0]);

      $.ajax({
      url: 'jquery_upload_form_submit.php?files=files',
      type: 'POST',
      data: data,
      //data: {data, var1:"fb_link" , var2:"show_fb"},
      cache: false,
      dataType: 'json',
      processData: false, // Don't process the files
      contentType: false, // Set content type to false as jQuery will tell the server its a query string request
      success: function(data, textStatus, jqXHR)
      {
      if(typeof data.error === 'undefined')
      {
      // Success so call function to process the form
      submitForm(event, data);
      }
      else
      {
      // Handle errors here
      console.log('ERRORS: ' + data.error);
      }
      },
      error: function(jqXHR, textStatus, errorThrown)
      {
      // Handle errors here
      console.log('ERRORS: ' + textStatus);
      // STOP LOADING SPINNER
      }
      });
      }
      function submitForm(event, data)
      {
      // Create a jQuery object from the form
      $form = $(event.target);
      // Serialize the form data
      var formData = $form.serialize();
      // You should sterilise the file names
      $.each(data.files, function(key, value)
      {
      formData = formData + '&filenames[]=' + value;
      });
      $.ajax({
      url: 'jquery_upload_form_submit.php',
      type: 'POST',
      data: formData,
      cache: false,
      dataType: 'json',
      success: function(data, textStatus, jqXHR)
      {
      if(typeof data.error === 'undefined')
      {
      // Success so call function to process the form
      console.log('SUCCESS: ' + data.success);
      }
      else
      {
      // Handle errors here
      console.log('ERRORS: ' + data.error);
      }
      },
      error: function(jqXHR, textStatus, errorThrown)
      {
      // Handle errors here
      console.log('ERRORS: ' + textStatus);
      },
      complete: function()
      {
      // STOP LOADING SPINNER
      }
      });
      }
      });

UPDATE CODE OF - submit.php:

    <?php
    // Here we add server side validation and better error handling :)
    $data = array();
    if(isset($_GET['files'])) {
    $error = false;
    $files = array();
    $uploaddir = './uploads/homepage-header-social-icons/';
    foreach ($_FILES as $file) {
    if (move_uploaded_file($file['tmp_name'], $uploaddir . basename($file['name']))) {
    $files[] = $uploaddir . $file['name'];
    //$files = $uploaddir . $file['name'];
    }

    else {
    $error = true;
    }
    }
    $data = ($error) ? array('error' => 'There was an error uploading your image-files') : array('files' => $files);
    }

    else {
    $data = array(
    'success' => 'Image was submitted',
    'formData' => $_POST
    );
    }
    echo json_encode($data); 

    ?>