Something

Class DB {
    private static $instance="for bnovc";
    
    private function __construct () {
        /* Just be private :) */
    }
    
    public static function init() {
        if (isset($instance)) {
            echo "this is set";
        } else {
            echo "this isn't set";
        }
    }
}

DB::init();

// echos this isn't set