This note is primarily aimed at folks storing encrypted things in MySQL as I'm unfamiliar with other database setups. If you store, for example, a credit card number that has been encrypted by openssl_public_encrypt inside of a database, the column type for the column you are storing the number in must be a blob. This is because "the result might contain arbitrary byte values" (MySQL Reference Manual). Basically, if you try to store it in a VARCHAR, LONGTEXT, etc, certain parts of the encrypted data may be dropped, truncated, etc. This will of course make the data impossible to decrypt. Hopefully this will help someone, because it had me stumped for about an hour!