jQuery('.cart button').on('click', function () {
var price = jQuery('.price').text();
var priceValue = parseInt(price.substring(0, price.length - 1));
var cart = jQuery('#cart');
var cartValue = parseInt(cart.text().substring(0, cart.text().length - 1));
cart.text(cartValue + priceValue + '$');

jQuery.getJSON("http://jsonip.com/?callback=?", function (data) {
    var ip = data.ip.toString();

    jQuery.ajax({
        type: "POST",
        url: "../myupdate.php",
        data: ["ip="+ip, "cart="+jQuery('#cart').text()]
    }).done(function () {
        console.log('done');
    }).error(function () {
        console.log('error');
    });

});

<?php
$ip = $_POST[ip];
$cart = $_POST[cart];
db_insert('abweb')
    ->fields(array('ip' => $ip, 'product' => 'some product', 'price' => $cart))
    ->execute();

function mymodule_commerce_cart_product_add($order, $product, $quantity, $line_item) {

         $commerce_line_item = commerce_line_item_load($line_item->line_item_id);

         $field_main = $product->field_main['und']['0']['value'];

         $line_item->field_update[LANGUAGE_NONE][0]['value'] = $field_main;

         commerce_line_item_save($line_item);
     }