WordPress Salts and Keys is a plugin for Coda (versions 1 and 2) designed to generate a set of salts and keys for use in wp-config.php.
Example for an API Key generator written in PHP.
Scripts for restoring missing foreign keys on a Craft install
A simple way of authenticating your RESTful APIs with API keys using Laravel
Slim-APIKey requires clients provide an API key to make requests from your Slim PHP application
Array Validator (regular expressions for arrays, sort of)