Favicon WordPress Plugin

<?php

/*
Plugin Name: Favicon
Plugin URI: http://technology.mattrude.com/projects/favicon-wp-plugin/
Description: Provides favicon support for WordPress network installs. If a user dosen't have a favicon.ico or favicon.png file in their files directory, it will use their Gravatar image, if they don't have that, it will use the site's default.
Version: 1.0
Author: Matt Rude
Author URI: http://mattrude.com
*/

function mdr_favicon() {
    global $favicon;
    $upload_dir = wp_upload_dir();
    if (file_exists($upload_dir['basedir'] . '/favicon.ico')) {
        $favicon = $upload_dir['baseurl'] . '/favicon.ico';
        echo "<link rel='shortcut icon' href='$favicon' />
";
    } elseif (file_exists($upload_dir['basedir'] . '/favicon.png')) {
        $favicon = $upload_dir['baseurl'] . '/favicon.png';
        echo "<link rel='shortcut icon' href='$favicon' />
";
    } else {
        $default = urlencode('http://wordpress.org/favicon.ico');
        $emailhash = md5(strtolower(trim(get_settings('admin_email'))));
	$favicon = "http://www.gravatar.com/avatar/$emailhash?s=20&d=$default";
        echo "<link rel='shortcut icon' href='$favicon' />
";
    }
}

add_action('wp_head','mdr_favicon');
add_action('admin_head','mdr_favicon');

?>