[Fou-Lu]

That can be fixed by checking the isset status:

PHP Code:

<?php

if (isset($_POST['name'], $_POST['size'], $_POST['gender']))
{
    $name=$_POST['name'];
    $size=$_POST['size'];
    $gender=$_POST['gender'];

    print "<p>Name: $name<br />Size: $size<br />Gender: $gender</p>";
}
else
{
    header('Location: http://yoursite.com/yourform.html');
    exit();
}
?>

Would do it. You'll get very familiar with the isset construct in PHP.