Code Mailchimp API on my PHP site

We have a PHP site with a MySQL database. We would like a button created using the Mailchimp Import function API which will allow us to add people to one of our Lists within Mailchimp, without them having to authorise the sign up. Please read through the attached document for full details and instructions, and feel free to ask any questions. You will be given full FTP and CPanel access to complete the job.