A small PHP challenge

flag.php

<?php
define('FLAG', 'flag{y0uW1n}');

index.php

<?php
require_once __DIR__ . '/flag.php';

$password = trim($_REQUEST['password'] ?? '');
$name = trim($_REQUEST['name'] ?? 'viewsource');
function viewsource() {show_source(__FILE__);}

if (strcmp(hash('sha256', $password), 'ca572756809c324632167240d208681a03b4bd483036581a6190789165e1387a') === 0) {
    function readflag() {
        echo FLAG;
    }
}

$name();
?>