title: WordPress hooks for executing right before any action or page loading
body: <p>I'm quite new to WP. Task is to develop a plugin for oauth authentication on one of not popular openID providers. I did the same for CodeIgniter project, but WP is a CMS and is little bit complex for me to understand. In Codeigniter i check authorisation before each action. In WP i need a hook which uses for it... before each page printing, or maybe.. it would be right to say before each action in terms of frameworks. What is this hook's name? </p>