The Paragon Initiative blog has posted a new article showing you how to safely implement cryptography in any PHP-based application (or really just about any application) with the help of libsodium.

Why not {Mcrypt, OpenSSL, Bouncy Castle, KeyCzar, etc.}? These cryptography libraries are really building blocks that by and large must be used, with expert care, to build the interfaces you want developers to use. In most cases, libsodium is the interface you want developers to use. [...] By default, these libraries don't provide [authenticated encryption](https://tonyarcieri.com/all-the-crypto-code-youve-ever-written-is-probably-broken). Most of them force developers to use RSA (or ECDSA but certainly not EdDSA), which is [hard to get right](http://www.daemonology.net/blog/2009-06-11-cryptographic-right-answers.html) and for which [index calculus attacks are improving each year](https://events.ccc.de/congress/2014/Fahrplan/system/attachments/2501/original/20141227.pdf).

He goes on to talk about NaCI as a possible option (libsodium is from a fork of it) but points out that NaCI isn't as easily available as libsodium to non-C/Python developers. He shares a few reasons why he thinks "libsodium is so great" and a few reasons not to use it (mostly dealing with outside limitations, not technical ones). Finally he points you in the right direction to help you get started using libsodium for PHP as a PECL extension.