Why this code isn't uploading image? - php

Question

Here is a code for uploading image using ajax. I have added jQuery library and jQuery form as well but this code neither gives me any error nor uploads image just uploading goes on and upload image starts running never to stop. Can't find whats wrong with this code.
upload.php
<script type="text/javascript" >
$(document).ready(function() {
$('#photoimg').live('change', function() {
$("#preview").html('');
$("#preview").html('<img src="./img/loader.gif" alt="Uploading...."/>');
$("#imageform").ajaxForm({
target: '#preview'
}).submit();
});
});
</script>
<form id="imageform" method="post" enctype="multipart/form-data" action='ajaximage.php'>
Upload your image <input type="file" name="photoimg" id="photoimg" />
</form>
ajaximage.php
<?php
include("/inc/connect.php");
if(isset($_SESSION['username'])) {
$username = $_SESSION['username'];
}
else if(isset($_COOKIE['username'])){
$username = $_COOKIE['username'];
}
else
{
//invalid ---
}
$path = "uploads/";
$valid_formats = array("jpg", "png", "gif", "bmp");
if(isset($_POST) and $_SERVER['REQUEST_METHOD'] == "POST")
{
$name = $_FILES['photoimg']['name'];
$size = $_FILES['photoimg']['size'];
if(strlen($name))
{
list($txt, $ext) = explode(".", $name);
if(in_array($ext,$valid_formats))
{
if($size<(1024*1024))
{
$actual_image_name = time().substr(str_replace(" ", "_", $txt), 5).".".$ext;
$tmp = $_FILES['photoimg']['tmp_name'];
if(move_uploaded_file($tmp, $path.$actual_image_name))
{
$sql=$db->prepare("UPDATE table SET profile_pic=:image_name WHERE username=:username");
$sql->execute(array(':image_name'=>$actual_image_name,':username'=>$username));
echo "<img src='uploads/".$actual_image_name."' class='preview'>";
}
else
echo "failed";
}
else
echo "Image file size max 1 MB";
}
else
echo "Invalid file format..";
}
else
echo "Please select image..!";
exit;
}
?>