PHP Singleton

<?php

class Settings {
    static public function instance () {
        static $resource = null;
        if(is_null($resource))
            $resource = new Settings();
        return $resource;
    }

    public $location = 'http://unknown/';

    final private function __construct () {}
}

// one file
$settings = Settings::instance();
$settings->location = 'http://www.e-mark.nl/';

// other file
$settings = Settings::instance();
echo $settings->location; // 'http://www.e-mark.nl/'