On the SitePoint PHP blog there's a new tutorial posted showing you how to use the Halite package to encrypt the contents of emails. The Halite library sits on top of the libsodium functionality to provide tested, hardened cryptographic results.
Cryptography is a complex matter. In fact, there is one golden rule: "Don’t implement cryptography yourself." The reason for this is that so many things can go wrong while implementing it, the slightest error can generate a vulnerability and if you look away, your precious data can be read by someone else.
[...] Some libraries out there implement cryptography primitives and operations, and leave a lot of decisions to the developer. [...] Nevertheless, there is one library that stands out from the rest for its simplicity and takes a lot of responsibility from the developer on the best practices, in addition to using the libsodium library. In this article we are going to explore Halite.
The tutorial then starts of helping you get the libsodium package installed on your system (assuming it's unix-based). They then start on the sample application - a basic "email" client able to send/receive messages between users. They set up RESTful endpoints to get the messages, use the Doctrine ORM for a database interface and show the use of the Halite
Crypto class to encrypt/decrypt the message contents.