User Registration form with facebook and normal way

I am in a process of making a website which has both php based simple website and along with it has a blog option. I want to make a custom user registration form which I have done in php. But I also want a facebook login button for my form in php.

The other problem I am facing is that when the user enters the b开发者_如何学运维log section he is out of the sign in section.

Can you please tell me a way through which my user remains signed in even when he enters the blog section.

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You never mentioned in the question, but since you tagged Wordpress I am assuming the blog is a Wordpress blog. There is a plugin that allows you to sign up with Twitter, Facebook or sign up with Wordpress as a third option. It sounds like something that would work for you.

http://mailchimp.com/social-plugin-for-wordpress/