using MCRYPT_ARCFOUR_IV

[yawnmoth]

<http://us.php.net/manual/en/ref.mcrypt.phpl ists MCRYPT_ARCFOUR and
MCRYPT_ARCFOUR_ IV. Both require a version of libmcrypt greater then
2.4.x. MCRYPT_ARCFOUR works just fine. MCRYPT_ARCFOUR_ IV does not.
The following demonstrates:

<?php
$td = mcrypt_module_o pen(MCRYPT_ARCF OUR, '', MCRYPT_MODE_STR EAM, '');
echo 'key size = '.mcrypt_enc_ge t_key_size($td) ."\r\n";
echo 'block size = '.mcrypt_enc_ge t_block_size($t d)."\r\n";
echo 'iv size = '.mcrypt_enc_ge t_iv_size($td). "\r\n";

echo "---";

$td = mcrypt_module_o pen(MCRYPT_ARCF OUR_IV, '', MCRYPT_MODE_STR EAM,
'');
echo 'key size = '.mcrypt_enc_ge t_key_size($td) ."\r\n";
echo 'block size = '.mcrypt_enc_ge t_block_size($t d)."\r\n";
echo 'iv size = '.mcrypt_enc_ge t_iv_size($td). "\r\n";
?>

What do I need to do to be asble to use MCRYPT_ARCFOUR_ IV? I'm
running PHP 5.2.2 on Windows XP. Thanks!