I have been using a site for the past few years which I wrote myself in PHP. The site was to create events for people to join and take part in, with different features in them for different events. Some were on subdomains of the main domain and some were on separate domains altogether. All of them were hosted on the same server and their account details held in the same MySQL database.
I am now moving to a WordPress site using WooCommerce to fulfill orders and entries so all future events will go through there. I know that the users will have to create a new password when they first use the WooCommerce/WordPress site as all of their details will be in a new database. Now I still have events that I wish to leave running which are not built around the WordPress site.
What I am trying to work out is;
How can I create a login script for the non-WP sites that will be able to login against the details from the WP user database? I don't understand how I too hash the details the same way as WP and confirm they are correct. Any links that can explain the hash that WP uses that I can understand?
What are the cookies/sessions that WP and WooCommerce set upon login so that I can search for them on the non-WP sites? If they log in on the main site I'd like for them to not have to log in again on the older sites.
I have been searching for answers all day and have only found little snippets of how parts might be possible. Changing some of the cookie settings in WP_config to set them for multiple sites has been one of them.
Any advice would be a huge help!