if (isset($_GET['mdp1']) and isset($_GET['mdp2'])) {
if ($_GET['mdp1'] != $_GET['mdp2'])
if (md5($_GET['mdp1']) === md5($_GET['mdp2']))
die('Congratulation , the flag is '.$flag);
else
print 'You did not make any collision ¯\_(ツ)_/¯';
}


Medium