PHP-Growl is an implementation of the Growl notification system written in PHP.
As a proof of concept example, I've written a Mint Pepper plugin that notifies you whenever certain events (like new referrals, unique visitors, etc) happen on your website. It's a slick way to stay on top of who is visiting your site. You can download Growl Pepper here.
<?PHP
$growl = new Growl($ip_address);
$growl = new Growl("workstation.example.com");
// Adding and registering your notifications with Growl
// only needs to be done once per computer. Growl will
// remember your app after this.
$growl->addNotification('Notification Name');
$growl->addNotification('Another Notification');
$growl->register();
// Send a notification
$growl->notify('Notification Name', 'Some Title', 'Some message to display');
// Send a second notification
$growl->notify('Another Notification', 'Another Title', 'Something useful I hope.');