server/submission.php

<?php

function show($file)
{
    if (file_exists($file))
        print file_get_contents($file);
    else
        header("Location: ".$_SERVER["HTTP_REFERER"]);
}

$file = __DIR__."/submission/".intval($_GET["team"])."-".intval($_GET["theme"])."-".urlencode($_GET["exercice"]);

if (file_exists($file))
    show(__DIR__."/teams/".intval($_GET["team"])."/submission-".intval($_GET["theme"])."-".urlencode($_GET["exercice"])."-already.html");

else if (!empty($_POST["solution"]) && !empty($_GET["team"]) && !empty($_GET["theme"]) && !empty($_GET["exercice"]))
{
    file_put_contents($file, $_POST['solution'], LOCK_EX);

    show(__DIR__."/teams/".intval($_GET["team"])."/submission-".intval($_GET["theme"])."-".urlencode($_GET["exercice"]).".html");
}

else
    show(__DIR__."/teams/".intval($_GET["team"])."/submission-".intval($_GET["theme"])."-".urlencode($_GET["exercice"])."-bad.html");