How to exploit the php_include($_GET['page']) vulnerability?

Question

PHP

The site has approximately the following hierarchy of files and folders

index.php
hello.php
папка out
----1.php
----2.php
----3.php
----папка pages
--------11.php
--------22.php
--------33.php

When you go to http://site/hello.php?page=11 , the contents of page 11.php are included inside
.
php_include("out/pages/".$_GET['page'].".php")
I can get to the folder above through this vulnerability) I tried page=../1 , it didn't work.

Answer 1

Maybe like this?)

if (filter_var($_GET['page'], FILTER_VALIDATE_INT)) 
        php_include("out/pages/".$_GET['page'].".php");

Answer 2

To understand whether there is a vulnerability or not, you need to see the code of the php_include function