即使在更改发送的数据后，AJAX也会显示相同的MySQL查询结果

Question

我正在运行一个AJAX函数，该函数将数据发送到运行MySQL查询并显示结果的页面。

此按钮单击启动功能

<div class="text-center">
    <button type="button" class="btn btn-sm btn-success" onclick="detailsmodal(<?php echo $product['id']; ?>)">Details</button>
</div>

这是AJAX功能

function detailsmodal(id){
    var data = {"id" : id};
    $.ajax({
        url : '/php-ecom/includes/details-modal.php',
        method : "post",
        data : data,
        success : function(data){
            $('body').append(data);
            $('#details-modal').modal('toggle');
        },
        error : function(){
            alert('something went wrong');
        }
    });
};

这是查询和显示数据库的URL

<?php
require_once '../core/init.php';

$id = $_POST['id'];
$id = (int)$id;
$sql = "SELECT * FROM products WHERE id = '$id' ";
$result = $db->query($sql);
$product = mysqli_fetch_assoc($result);
$brand_id = $product['brand'];
$sql2 = " SELECT brand FROM brand WHERE id = '$brand_id' ";
$brand_query = $db->query($sql);
$brand = mysqli_fetch_assoc($brand_query);
$sizestring = $product['sizes'];
$size_array = explode(',', $sizestring);
?>
<?php ob_start(); ?> 

<div class="modal fade details-1" id="details-modal" tabindex="-1" role="dialog" aria-labelledby="details-1" aria-hidden="true">
    <div class="modal-dialog modal-lg">
        <div class="modal-content">
            <div class="modal-header">
                <button class="close" type="button" onclick = "closeModal()" aria-label="Close">
                     <span aria-hidden="true">&times;</span>
                </button>
                <h4 class="modal-title text-center"><?php echo $product['title']; ?></h4>
            </div>
            <div class="modal-body">
                <div class="container-fluid">
                    <div class="row">
                        <span id="modal_errors" class="bg-danger"></span>
                        <div class="col-sm-6">
                            <div class="center-block">
                                <img src="<?php echo $product['image']; ?>" alt="<?php echo $product['title']; ?>" class="details  img-responsive">
                            </div>
                        </div>
                        <div class="col-sm-6">
                            <h4>Details</h4>
                            <p><?php echo $product['description']; ?></p>
                            <hr>
                            <p>Price: <?php echo $product['list_price']; ?></p>
                            <p>Brand: <?php echo $brand['brand']; ?></p>
                            <form action="add_cart.php" method="post" id="add_product_form">
                                <input type="hidden" name="product_id" value="<?=$id; ?>">
                                <input type="hidden" name="available" id="available" value="">
                                <div class="form-group">
                                    <div class="col-xs-3">
                                        <label for="quantity">Quantity:</label>
                                        <input type="number" class="form-control" id="quantity" name="quantity">

                                    </div>
                                    <p>Available: 3</p>
                                </div><br>
                                <div class="form-group">
                                    <label for="size"></label>
                                    <select name="size" id="size" class="form-control">
                                        <option value="">options</option>
                                        <?php foreach($size_array as $string){
                                            $string_array = explode(':',$string);
                                            $size = $string_array[0];
                                            $available = $string_array[1];
                                        ?>
                                        <option value="<?php echo $size; ?>" data-available="<?=$available ?>"><?php echo $size; ?>  (Available: <?php echo $available; ?>)</option>
                                        <?php }; ?>
                                    </select>
                                </div>
                            </form>
                        </div>
                    </div>
                </div>
            </div>
            <div class="modal-footer">
                <button class="btn btn-default" onclick="closeModal()">Close</button>
                <button class="btn btn-warning" onclick="add_to_cart(); return false;"><span class="glyphicon glyphicon-shopping-cart"></span> Add To Cart </button>
            </div>
        </div>
    </div>
</div>
<script>
    $('#size').change(function(){
        var available = $('#size option:selected').data('available');
        $('#available').val(available);
    });

    function closeModal(){
        $('#details-modal').modal('hide');
        setTimeout(function(){
            $('#details').remove();
            $('.modal-backdrop').remove();
        },500);
    };
</script>

<?php echo ob_get_clean();   ?>

问题在于即使我发送不同的数据，我也得到相同的MySQL结果。