<?php

class FooBar {
    public static function doTheFoo() {
        return 'foobar';
    }
}

Warning  (XHP87) Class Not `abstract` Or `final`
 This class is neither `final` nor `abstract`, and does not have a
 docblock marking it `@concrete-extensible`.

            1 <?php
            2
 >>>        3 class FooBar {
            4     public static function doTheFoo() {
            5         return "foobar";
            6     }