Not able to upload image via jquery, ajax and PHP - php

Question

I have fair knowledge of JS, PHP and Ajax but this simple problem has driven me nuts.
I am trying to upload an image silently, without using a form. I am not using a form because that will lead to nested forms in my HTML, which I read, can cause additional issues.
I have been able to use oFReader, to preview the images.
To upload the image, I am attempting an AJAX call as given below:
HTML
<div id="loginButton2">
<div id="personalimg" >
<img src="photos/seller_photos/<?php echo $profile_pic; ?>" width="70" hight="70" />
</div>
</div>
<div id="loginBox2" style="display:none">
<div id="loginForm2" class="floatLeft" >
<fieldset>
<input id="file" type="file" name="profile_img" value="photos/seller_photos/<?php echo $profile_pic;?>"/>
<input id="file_submit" type="hidden" name="submit4" value="1" >
</fieldset>
</div>
</div>
JS
$('#file').change(function(){
var oFReader = new FileReader();
oFReader.readAsDataURL(this.files[0]);
var fd = new FormData();
var file = $("#file").prop("files")[0];
fd.append('profile_img', file);
fd.append('submit4', 1);
fd.append('filename', 1);
oFReader.onload = function (oFREvent) {
$.ajax({
url: "upload.php",
dataType: 'image',
cache: false,
contentType: false,
processData: false,
type: "POST",
data: fd,
success: function(data){
console.log(data);
},
error: function(){
console.log("image upload failed");
}
});
$('#loginForm2').toggle();
$('#personalimg').html('<img src="'+oFREvent.target.result+'" width="70" height="70">');
};
});
PHP
if(isset($_POST['submit4'])) {
$check_sql = "select profile_pic from profile where user_id=$user_id";
$check_rs = mysql_query($check_sql);
$check_num = mysql_num_rows($check_rs);
if($check_num==0) {
$sql = "insert into profile(user_id) values($user_id)";
$rs = mysql_query($sql);
}
$fName = $_FILES["profile_img"]["name"] ;
$data = explode(".", $fName);
$fileName = $user_id.'.'.$data[1];
if($fName!='')$user->update('profile_pic',$fileName);
$fileTmpLoc= $_FILES["profile_img"]["tmp_name"];
//image store path
$pathAndName = "photos/seller_photos/".$fileName;
$moveResult = move_uploaded_file($fileTmpLoc, $pathAndName);
if(move_uploaded_file) {
$response['status'] = '1';
header('Location: edit_profile_new.php');
} else {
$response['status'] = '0';
}
return $response;
}
But somehow, I have not been able to get this to work. I am using chrome. I get 302 Found status code and "image upload failed" in console.
Can someone please help me out?
ps: I know, mysql is deprecated and will migrate to pdo. This code is inherited and hence has old standards.