A page that takes a post redirects the browser to a plain page, so a refresh cannot post twice - and then the page the browser lands on has to say what happened. A flash message carries that: padFlash ( 'Thanks, your message was sent.' ) before the padRedirect (), and {flash} on the page it leads to.

<?php

  padFlash ( 'Your message was sent.', 'success' );

?>

{flash}
  <p class="notice {$type}">{$message}</p>
@else@
  <p>Nothing to report.</p>
{/flash}

• {flash} renders its content once per message, with {$message} and {$type}; without a message the @else@ half renders. {flash 'error'} shows the messages of that type only.
• The type is the second argument of padFlash, info when it is left out.
• A message lives exactly one request after the one that flashed it - the redirect's destination - and is gone after that, shown or not. A page that flashes and renders itself shows it at once, as here.
• The message is kept in the session, which starts on demand. A small padFlash cookie tells the next request that there is something to take, so the pages that never flash do not open the session at all.