php send/submit , refreshing can spam

[AsiaUnderworld]

Hi, ive got some simple code, kind of a guestbook like thing where people can type their name and message and post it, however if you hit refresh, it sends it again, so you can spam, any way of me stopping this?

 

<?php

if(isset($_POST['submit']))

{

$name = mysql_real_escape_string($_POST['name']);

 

$msg = mysql_real_escape_string($_POST['msg']);

 

if (strlen($name) < 1)

echo "<div align=center>Please enter your name</div>";

elseif(strlen($msg) < 1)

echo "<div align=center>Please Enter a message</div>";

else

{

$sql =  mysql_query("INSERT INTO guest (postername,content) VALUES ('$name','$msg')");

 

if($sql)

echo "<div align=center>Message posted</div>";

else

echo "<div align=center>There was a problem.</div>";

}

}

?>

[ricmetal]

of what i understand:

either use re-captcha (or any other interface, as long as the user has to type in something diferent every time they refresh the page),

or send the user to another page where refreshing doesnt interfere with the submition form