_addItem.php

<input id="qty" type="text" value="" name="qty[]">
<input id="upc" type="text" value="" name="upc[]" disabled>
<input id="name" type="text" value="" name="name[]" disabled>
<input id="price" type="text" value="" name="price[]" disabled>
<input id="extprice" type="text" value="" name="extprice[]" disabled>

<br/>

add.php

<?php
//Just an example, not production
$product = array('upc'=>'1234','price'=>1,'name'=>'Internets');
echo json_encode($product);

create.php

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script type="text/javascript">
    $(document).ready(function(){
        function getProduct(str) {
            $.ajax({
                url: 'sale/add.php',
                data: 'query='+str,
                dataType: 'json',
                success: function(data) {
                    $('.upc').val('');
                    $('#cart').append(
                        $('<div />').load('views/sale/_addItem.php',function(){
                            $('#qty').val('1');
                            $('#upc').val(data['upc']);
                            $('#name').val(data['name']);
                            $('#price').val(data['price']);
                        })
                    );//"Name: " + data['name']);
                    return false;
                },
                error: function() {
                    $('.upc').val('');
                    alert('No product found!');
                }
            });

        }
        $( ".sale-add-button" ).click(function() {
            getProduct($('.upc').val());
        });

        $('.upc').bind("enterKey",function(e){
            getProduct($('.upc').val());
        });
        $('.upc').keyup(function(e){
            if(e.keyCode == 13){
                $(this).trigger("enterKey");
            }
        });

    });
	</script>
<h1>Point of sale</h1>

    <input type="text" class="upc input-medium" placeholder="UPC" name="upc" autocomplete="off" >

    <button type="submit" class="sale-add-button btn">Add to Cart</button>

<form class="form-inline" method="POST" action="index.php?action=sale/add">
<div id="cart">

</div>
</form>