Yii Backend Embed Login On Existing Php Website

Hello, I have built a backend using Yii that both our users and staff can login to. However, our existing site is just a site built on PHP, not using Yii. Is there anyway I can do the following:

1.) Embed a login section at the top of our existing php site to log the users into the backend or create an account for the backend?

2.) Know that the user is logged in to the Yii Backend on the existing php site and display there name or username with a link to their profile?

Any help would be greatly appreciated. Thank you in advance.