RRSlug is a PHP library which aims to turn any kind of text into an URL friendly string.
<?php
// Include the autoloader.
require_once( dirname( __FILE__ ) . '/Classes/RRSlug.class.php' );
$slugifier = new RRSlug();
$text = 'Vous êtes les bienvenus!';
$slug = $slugifier->filter( $text );
print $slug; // Output: 'vous-etes-les-bienvenus'
The code is licensed under the very liberal MIT license.