var canvas = document.getElementById("theCanvas");
var img = canvas.toDataURL("image/png");
$.ajax({
    type: 'POST',
    url: 'http://********/ImageUpload.php',params: {img: img},

    success: function (msg)
    {
        alert("Done, Picture Uploaded.");
    }
});

<?php
define('UPLOAD_DIR', '/pic');
$img = $_POST['img'];
$img = str_replace('data:image/png;base64,', '', $img);
$img = str_replace(' ', '+', $img);
$data = base64_decode($img);
$file = UPLOAD_DIR . uniqid() . '.png';
$success = file_put_contents($file, $data);
print $success ? $file : 'Unable to save the file.';
?>

$query = "INSERT INTO item(title, description, price) values('".$_GET['title']."', '".$_GET['description']."', ".$_GET['price'].")";

$stmt = $conn->query($query);
$item_id = mysql_insert_id($conn);

$query = "INSERT INTO item_pic(path, item_id) values('".$_GET['path']."', '".$_GET['item_id'].")";

$stmt = $conn->query($query);

$.ajax({
 type: "POST",

 url: "http://*****/*****/AddProduct/create.php?title="+ ($("#myTitle").val())+"&description="
 +$("#myDesc").val()+"&price="+$("#myPrice").val(),
 success: function(data){
    alert("inserted");
 }});