PHP Flash messages

Mostly useful if you're using a framework or CMS.

At the top of your page:

if ( $_SESSION['notice'] ) {
    print $_SESSION['notice'];
    unset( $_SESSION['notice'];
}

To add a message:

$_SESSION['notice'] = "Hello, world!";

This message will show up on the next page load, and you can make the message persistant by removing the unset(...) line.