Newbie PHP help

I am fairly new to PHP and the following is a script I found on http://php.resourceindex.com. It is a "Tell a friend" script which works perfectly but I need to change something, when the user hits the submit button it forwards them to a basic text page saying "thanks" this seems to be done by the ECHO section near the bottom of the script, I would like to change this so that it goes to a HTML/PHP page that I specify instead (friend_suc.html) :

You can see exactly how the script currently works by going to http://gd.project77.net/friend.php

<script language="php">
$nameX = stripslashes($name);
$to_nameX = stripslashes($to_name);
$url = "http://www.randomportal.com";
$message = "Hello $to_nameX,
I think you would like $url";
$subject = "$nameX wants you to check this site out";

if (( $to_email_address) && ( $from_email_address)) {

mail($to_email_address, $subject, $message,
"From: $from_email_address
Reply-To: $from_email_address
X-Mailer: PHP
Errors-To: $from_email_address");
echo "Thank you"; <---- This is what I want to change
} else {

echo "error";
}

</script>