[鹤城杯 2021]EasyP

php
include 'utils.php';

if (isset($_POST['guess'])) {
$guess = (string) $_POST['guess'];
if ($guess === $secret) {
$message = 'Congratulations! The flag is: ' . $flag;
    }else {
$message = 'Wrong. Try Again';
    }
}

if (preg_match('/utils\.php\/*$/i', $_SERVER['PHP_SELF'])) {
exit("hacker :)");
}

if (preg_match('/show_source/', $_SERVER['REQUEST_URI'])){
exit("hacker :)");
}

if (isset($_GET['show_source'])) {
highlight_file(basename($_SERVER['PHP_SELF']));
exit();
}else{
show_source(__FILE__);
}
?>