update.php

 <?php

require_once 'include/DB_Functions.php';
$db = new DB_Functions();

// json response array
$response = array("error" => FALSE);

if (isset($_POST['unique_id']) && isset($_POST['name']) && isset($_POST['username']) && isset($_POST['used_username']) && isset($_POST['image'])) {

    // receiving the post params
    $unique_id = $_POST['unique_id'];
    $name = $_POST['name'];
    $username = $_POST['username'];
    $used_username = $_POST['used_username'];
    $image = $_POST['image'];

    //check if username is not change
    if($username == $used_username){
        $user = $db->updateUser($unique_id, $name, $username, $image);
        if ($user) {
            // user stored successfully
            $response["error"] = FALSE;
            $response["uid"] = $user["unique_id"];
            $response["user"]["name"] = $user["name"];
            $response["user"]["username"] = $user["username"];
            $response["user"]["previllage"] = $user["previllage"];
            $response["user"]["created_at"] = $user["created_at"];
            $response["user"]["updated_at"] = $user["updated_at"];
            echo json_encode($response);
        } else {
            // user failed to store
            $response["error"] = TRUE;
            $response["error_msg"] = "Unknown error occurred in registration!";
            echo json_encode($response);
        }
    }else{
        // check if user is already existed with the same username
        if ($db->isUserExisted($username)) {
            // user already existed
            $response["error"] = TRUE;
            $response["error_msg"] = "User already existed with " . $username;
            echo json_encode($response);
        } else {
            // create a new user
            $user = $db->updateUser($unique_id, $name, $username, $image);
            if ($user) {
                // user stored successfully
                $response["error"] = FALSE;
                $response["uid"] = $user["unique_id"];
                $response["user"]["name"] = $user["name"];
                $response["user"]["username"] = $user["username"];
                $response["user"]["previllage"] = $user["previllage"];
                $response["user"]["created_at"] = $user["created_at"];
                $response["user"]["updated_at"] = $user["updated_at"];
                echo json_encode($response);
            } else {
                // user failed to store
                $response["error"] = TRUE;
                $response["error_msg"] = "Unknown error occurred in registration!";
                echo json_encode($response);
            }
        }
    }
} else {
    $response["error"] = TRUE;
    $response["error_msg"] = "Required parameters is missing!";
    echo json_encode($response);
}
?>