<?php
$td = @mcrypt_module_open('rijndael-256', '', 'cfb', '');

if ($td) {
    /* Get key size and IV size */
    $iv_size  = mcrypt_enc_get_iv_size($td);
    $key_size = mcrypt_enc_get_key_size($td);

    /* Create IV and 'key' */
    $iv  = mcrypt_create_iv($iv_size);
    $key = substr(sha1('very secret key'), 0, $key_size);

    /* Init encryption module */
    mcrypt_generic_init($td, $key, $iv);
}
?>