$(document).ready(function() {

    $('a.add_to_shoppin_cart').click(function () {

        var product_id = $(this).attr('rel');

        $.ajax({
            type: 'post',
            async: true,
            url:  '/?page=shopping_cart',
            data: 'action=add_to_shopping_cart&product_id='+product_id,
            success: function(data) {

            }
        });

        return false;

    });

});