What to add to the basket file via AJAX?

Question

PHP

Hello. The site has a basket, you need to do it without reloading. After three days of picking, I realized that I could not do without help.
HTML code:

<form id="formCart" action="javascript:void(null);">
        <input class="hitNameBasket" type="hidden" name="hitName" value="<?=$Element['NAME'];?>" />
        <input class="hitPriceBasket" type="hidden" name="hitPrice" value="<?=$Element['PRICE'];?>" />
        <a href="#" class="hitToBasket" data-id="<?=$Element['ID'];?>">В корзину</a>
</form>

AJAX code:

$('.hitToBasket').click(function(e){
    e.preventDefault();
    var dataId = $(this).data('id');
    var dataName = $('.hitNameBasket').val();
    var dataPrice = $('.hitPriceBasket').val();
    $.ajax({
      type: 'POST',
      url: '<?require_once($_SERVER["DOCUMENT_ROOT"]."/template/cart.php");?>',
      data: {id: dataId},
      success: $('.orderName').text(dataId),
    });
  });

Now the ID is passed to .orderName, but it disappears when the page is reloaded.
I don't see what print_r($_POST); Empty array.
AJAX links to cart.php
What should be in this file? What is the logic? Where to dig? If possible, in more detail.
Thank you very much in advance.

Answer 1

What is this design anyway?
url: '<?require_once($_SERVER["DOCUMENT_ROOT"]."/template/cart.php");?>',
This should be a link like example.com/cart.php and not some kind of cart template.
And in this file you need to handle your $_POST.

Answer 2

Here is an example for Bitrix for NOT programmers) there is only one meaning, you can take it as a basis