使用PHP使用HTTPS协议从表单插入数据

So I'm developing a simple Facebook contest page using an iFrame with HTTPS since Facebook use this protocol. Users enter some informations and everyone participating are registered in our database.

At first, I developed a short form using the PHP request ($_SERVER["REQUEST_METHOD"] == "POST"). My application wasn't on a HTTPS secured domain, so everything was working fine. Then I copied the same page in the HTTPS domain so that it could work inside a Facebook tab. Now my Mysql queries are sending errors. I tried to find a tutorial where it explains how to retrieve informations from a PHP form using HTTPS protocols and inserting them inside a local database but I found nothing.

How can I achieve this?

Thanks !