PGP confusion

[Pig]

I need to encrypt a file with PGP, but I am lost. I am trying to follow this script: http://www.alt-php-faq.org/local/65/

My scenario is a little different that this snippt is using. I have the public of key for the person that will ultimately recieve the file. I don't care about creating or using a key pair for myself, just encrypting this file before it is sent off. I have this file uploaded to the server, as well as file that needs to be encrypted. How can I modify this script to do what I need?

Also, the script refers the pgp location on the server as "/usr/local/bin/gpg". I don't have that, so I did a locate, and got a ton of results. I am posting the most relevant ones (I think) below. Which one should I use for the pgp location?

/usr/bin/lspgpot
/usr/bin/pgpewrap
/usr/bin/pgpring
/home/username/public_html/.pgp

Thanks to whoever keeps me from bleeding out my ears.

Here is the script itself:

<?php
//Set the username to the user on the server 
$username = "thepurpl"; 

$pgp="/usr/local/bin/gpg"; 

// User that is sending the e-mail (In the from address etc..) 
$user="Darren Casey <[e-mail]>"; 

//This is the key that was uploaded, i.e. the recipent of the PGP message 
$recp="First Last <[e-mail]>"; 

$data="Text that will be encrypted"; 


$command = 'echo "'.$data.'" | '.$pgp.' -a --always-trust --batch --no-secmem-warning -e -u "'.$user.'" -r "'.$recp.'"'; 

$oldhome = getEnv("HOME"); 

putenv("HOME=/home/$username"); 
$result = exec($command, $encrypted, $errorcode); 
putenv("HOME=$oldhome"); 

$message = implode("\n", $encrypted); 
if(ereg("-----BEGIN PGP MESSAGE-----.*-----END PGP MESSAGE-----",$message)) 
{ 
        echo "It Worked"; 
}else 
{ 
        echo "It failed"; 
} 
$subject="Test message"; 
$header="From: $user"; 

echo "Message<br>"; 
echo nl2br($message); 

mail($recp,$subject,$message,$header); 
?>