Need Salesforce API detail to create lead in salesforce CRM from my website(PHP)

Friends,

I have a contact us/Inquiry form in my website. I want to generate a lead in Sales force CRM on submission of this form.

What I have tried ?

I have checked in salesforce doc and Google it I found something

http://wiki.developerforce.com/page/REST_API

http://www.salesforce.com/us/developer/docs/api/index.htm

But I did not get clear documentation for integrating it with PHP.

If any one integrated this please help me out !!

Thanks !!

Note: I have worked with force.com and salesfoce.com so i can understand foce.com API easily but i am not getting any link for API.