I know this script works because they used it last year to mail christmas cards to a large number of recipients who are listed in semi colon delimited text file. I have the mailer and here it is. When I sign on to the slice to run linux commands, how do I execute this script?

and how to get it to take in all the names. This is an e-card.
<?php
switch($_POST["mailtime"]){
default:
echo "<form action=\"mailer.php\" method=\"post\">
<input type=\"text\" size=\"77\" name=\"mailToAddress\"/>
<br><input type=\"submit\" value=\"Send HTML x-mas card\"/>
<input type=\"hidden\" value=\"mailtime\" id=\"mailtime\" name=\"mailtime\"/>
</form>";
break;
case "mailtime":
sendmessage();
break;
}
function sendmessage(){
$mailToAddress = $_POST["mailToAddress"];
// add From: header
$headers = "From: dszeto@govanbrown.com\r\n";
// reply to
$headers .= "Reply-To: dszeto@govanbrown.com\r\n";
// specify MIME version 1.0
$headers .= "MIME-Version: 1.0\r\n";
// unique boundary
$boundary = uniqid("HTMLDEMO");
// tell e-mail client this e-mail contains alternate versions
$headers .= "Content-Type: multipart/alternative" . "; boundary = $boundary\r\n\r\n";
// mesage to people with clients who don"t understand MIME
$headers .= "This is a MIME encoded message.\r\n\r\n";
// plain text version of message
$headers .= "--$boundary\r\n" . "Content-Type: text/plain; charset=ISO-8859-1\r\n" . "Content-Transfer-Encoding: base64\r\n\r\n";
$headers .= chunk_split(base64_encode("Seasons Greetings,
// HTML version of message
$headers .= "--$boundary\r\n" . "Content-Type: text/html; charset=ISO-8859-1\r\n" . "Content-Transfer-Encoding: base64\r\n\r\n";
$headers .= chunk_split(base64_encode("<html>
<head> etec etc
</html>"));
$sentTo .= "$mailToAddress\r\n";
// send message and check it
if(mail($mailToAddress, "Seasons Greetings", "", $headers)){
echo "<form action=\"mailer.php\" method=\"post\">
<input type=\"text\" size=\"77\" name=\"mailToAddress\"/>
<br><input type=\"submit\" value=\"Send HTML x-mas card\"/>
<input type=\"hidden\" value=\"mailtime\" id=\"mailtime\" name=\"mailtime\"/>
</form>";
echo "message sent to $sentTo";
} else {
echo "the email has not been sent";
}
}
?>
THANKS FOR ANY HELP!!