使用POST类型的Ajax FormData但在PHP文件中无法获取请求

I am unable to figure out the problem .I apology in advance if I have lack of knowledge and did silly mistakes. Here is my piece of code.

    <!-- Piece of html -->
    <div class="form-group">
    <input class="form-control" placeholder="Enter Service image" id="edit_service_image-1" type="file" name="file_image">
    </div>
    <button type="button" class="btn btn-primary" onclick="processIt(<?php echo $service['service_id'];?>,'esi',document.getElementById('edit_service_image-1').files[0])">Edit</button>

The javascript function :->

    function processIt(id,flag,inputvalue)
    {

         var filedata = new FormData();
         filedata.append('imagefile', inputvalue);
         filedata.append('id', id);
         filedata.append('flag', flag);
         $.ajax({
                    url: 'modify.php',
                    type: 'POST',
                    inputvalue: filedata,
                    contentType: false,
                    processData: false,
                    cache: false
                }).success(function(msg) {
                    alert(msg);
                });


    }

Here is modify.php (Only test code)

    <?php
      if(isset($_REQUEST['flag']) && !empty($_REQUEST['flag']) && isset($_REQUEST['id']) && !empty($_REQUEST['id']) )
        {
         $flag = $_REQUEST['flag'];
         $id = $_REQUEST['id'];
         echo "Processed";
        }
       else
        echo "Request not processed";
    ?>

So my problem is its always alerting "Request Not Processed", which means nothing is getting posted using ajax POST . I am confused, couldn't figure out the exact problem.

Edit

Another test code of modify.php

     <?php
        print_r($_FILES);
        print_r($_POST);
     ?>

In this case the output is -->

    Array{

    }
    Array{

    }

SOLVED

Thanks to everybody who guided me Just a change in javascript worked . Here's the following changed code in processIt() function, which served my purpose->

 function processIt(id,flag,inputvalue)
    {

         var filedata = new FormData();
         filedata.append('imagefile', inputvalue);
         filedata.append('id', id);
         filedata.append('flag', flag);
         $.ajax({
                    url: 'modify.php',
                    type: 'POST',
                    data: filedata, // Here instead of inputvalue it's changed to data
                    contentType: false,
                    processData: false,
                    cache: false
                }).success(function(msg) {
                    alert(msg);
                });


    }