Why is mcrypt_encrypt giving errors?
<p>I got the code below from this site. When I run it, I get</p>

<pre><code>Warning: mcrypt_encrypt(): Attempt to use an empty IV, which is NOT recommend in C:\web\apache\htdocs\dev\encrypt.php on line 7
</code></pre>

<p>What wrong am I doing here and how do I get this right?</p>

<pre><code>//Key

$key = 'SuperSecretKey';

//To Encrypt:
$encrypted = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, 'I want to encrypt this', MCRYPT_MODE_CFB);

//To Decrypt:
$decrypted = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $encrypted, MCRYPT_MODE_CFB);

echo $encrypted;
echo "&lt;br&gt;";
echo $decrypted;
</code></pre>
