hey,
Greeting of the day,
I read your description carefully and what i have understood from this description that you need someone who can integrate shopping cart and payment gateway API integration in your website.
i have 4 year experience in this field.I know all the measure problem regarding to PHP and Ecommerce.
All i want to say that i am the right person for your project.
i will give the result in given time and budget.
If you are interested than revert me back so that we can discuss further. Thank you