Should mention this, though I think its unimportant. When I 'view source' of contactus.php live on the web the php code above the doc type tag is not visable. Is that correct?
Yes that is correct. The server acts upon the PHP code and renders it (where appropriate) as HTML. If no HTML is rendered then it shows nothing in "View source"
<?php echo "Hello World"; ?>
would just show as plain "Hello World" without the PHP code. This is true whether it's above or below the doc type tag. Although you wouldn't, of course, have my example outside of the body tag but the principle is the same.