<?php
// dangerously simple PHP regular expression URL router
// requires a mod_rewrite like "RewriteRule . /index.php [L]"

function get($url, $callback) {
    $matches = array();
    if (preg_match('~' . $url . '~', $_SERVER['REQUEST_URI'], $matches)) {
        echo call_user_func_array($callback, $matches);
        die();
    }
}

get('foo', function($url) {
    return 'you got foo';
});

get('bar([\d])', function($url, $digit) {
    return 'bar number ' . $digit;
});

get('.*', function() {
    return 'catch all. try /foo or /bar[0-9]';
});