product-add.php

<?php
require_once 'templates/header.php';
?>

    <script type="text/javascript">
        function fetch_select(val)
        {
            $.ajax({
                type: 'post',
                url: 'fetch_data.php',
                data: {
                    get_option:val
                },
                success: function (response) {
                    document.getElementById("new_select").innerHTML=response;
                }
            });
        }
    </script>

    <div class="content">
        <div class="container-fluid">
            <div class="row">
                <div class="col-sm-5">
                    <div class="form-group">
                        <select class="form-control" onchange="fetch_select(this.value);" name="category_id">
                            <option value="empty">Kategorijos Pavadinimas</option>
                            <?php
                            $categoryShow = $categories->categoriesShow();
                            if ($categoryShow)
                            {
                                while ($result = $categoryShow->fetch_assoc())
                                {
                                    ?>
                                    <option value="<?php echo $result['category_id']; ?>"><?php echo $result['category_name']; ?></option>
                                    <?php
                                }
                            }
                            ?>
                        </select>
                    </div>
                    <div class="form-group">
                        <select class="form-control" id="new_select">
                            <option value="empty">Subkategorijos Pavadinimas</option>
                        </select>
                    </div>
                </div>
            </div>
        </div>
    </div>

<?php
require_once 'templates/footer.php';
?>