Decrypting with different IV - php

Question

I've found a pair of encryption and decryption functions that look like they obey all the rules of data security that I'm desperate to fully understand but probably won't be able to without a doctorate in this stuff.
They work great when I'm encrypting and decrypting something on the same page with the same IV.
But when I try saving the results to an SQL database and then pulling them back out again and decrypting, it doesn't work.
$key = "secretsecret";
$iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC), MCRYPT_DEV_RANDOM);
function encrypt($key, $text, $iv) {
return trim(base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $text, MCRYPT_MODE_CBC, $iv)));
}
function decrypt($key, $text, $iv) {
return trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, base64_decode($text), MCRYPT_MODE_CBC,$iv));
}
$text = "the text to encrypt";
echo "Plain Text: " . $text . "<br><br>";
$encrypted = encrypt($key, $text, $iv);
echo "Encrypted Text: " . $encrypted . "<br><br>";
echo "Decrypted Text: ". decrypt($key, $encrypted, $iv) . "<br><br>"; //this works fine
//save encrypted text to SQL
mysql_query("UPDATE table SET test='".addslashes($encrypted)."' WHERE id='1'");
Then if on another page view I pull the text back out and try to:
echo "Decrypted Text: ". decrypt($key, $textFromSQL, $iv) . "<br><br>";
I get gibberish. What do I need to do to get the text decrypted properly with a different IV?

Answer 1

You need to use the same Initialization Vector (IV) in the decryption as you do in the enryption. This means you need to store the IV in the database.
The IV doesn't need to be secret, unlike the key.
Something like this:
mysql_query("UPDATE table SET test='".addslashes($encrypted)."', IV='".addslashes($IV)."' WHERE id='1'");
Then when you decrypt the data use the stored IV.