<?php
if (isset($_GET["nb"])) {
$nb = (int)$_GET["nb"];
if ($nb < 0 and $nb > 100)
$nb = null;
} else
$nb = null;
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Hello World 2</title>
</head>
<body>
<ul>
<?php
if ($nb !== null) {
for ($i = 0; $i < $nb; $i++) { ?>
<li>Hello World !</li>
<?php }
} else { ?>
<strong>Invalid number !</strong>
<?php } ?>
</ul>
</body>
</html>