<?php
include('Crypt/RSA.php');

$rsa = new Crypt_RSA();
$rsa->loadKey('...'); // public key

$plaintext = '...';

//$rsa->setEncryptionMode(CRYPT_RSA_ENCRYPTION_OAEP);
$ciphertext = $rsa->encrypt($plaintext);

$rsa->loadKey('...'); // private key
echo $rsa->decrypt($ciphertext);
?>