Hi,
I have an existing non-Drupal web app, with its own user repository and login process. I now need to deploy a Drupal site, for use by the same users, that will be automatically accessible to any users who have already logged-in to their original web app account.
The original web app provides a SOAP API, and some PHP includes which allow me to ask the main web app "is the current user logged in". This function will either return an array of the user details (username, real name, email etc) if the user is logged-in, or will redirect to the original web app login page otherwise.
I've been instructed to invoke the "is the current user logged in" function at the point that any page is requested from my Drupal app. Which hook should this call be placed in to ensure it is invoked for every page requested, before any content is sent back to the HTTP stream?