<form action="delivery_add.php" method="POST" id="forms">
                        <div class="form-group">
                            <label>Delivery Receipt: </label>
                            <input type="number" name="Receipt" class="form-control" />
                        </div>

                        <div class="form-group">
                            <label>Delivery Date: </label>
                            <input type="date" name="Date" class="form-control" />
                        </div>

                        <div class="form-group">
                            <label>Supplier Name:</label>
                            <select name="Supplier" class="form-control">
                                <?php
                                    include('config.php');
                                    $sql = "SELECT Supplier_ID, Supplier_Name FROM tbl_supplier";
                                    $result = mysql_query($sql);
                                    while ($row = mysql_fetch_array($result)) {
                                        echo "<option value=".$row[0].">";
                                        echo $row[1];
                                        echo "</option>";
                                    }
                                ?>
                            </select>
                        </div>

            <a id="clickbtn" class="btn btn-default">Add Item</a>
            <button type="submit" class="btn btn-default">Process</button>
                 <div class="form-group">
                <table class="table table-bordered table-hover"><br/>
                            <tr>
                                <td width="250">
                                    <label>Product Name:</label>
                                </td>
                                <td width="100">
                                    <label>Delivered Quantity:</label>
                                </td>
                                <td width="200">
                                    <label>Price:</label>
                                </td>
                            </tr>
                </table>
                    <div id="form-sample">
                        <table class="table table-bordered table-hover">
                            <tr>
                                <td width="250">
                                    <select name="Product_ID[]" class="form-connect" id="pta" onchange="myFunction(this)">;
                                    <?php
                                        $sql = "SELECT Product_ID, Product_Name FROM tbl_product";
                                        $result = mysql_query($sql);
                                        while ($row = mysql_fetch_array($result)) {
                                            echo "<option value=".$row[0].">";
                                            echo $row[1];
                                            echo "</option>";
                                        }
                                    ?>
                                    </select>
                                </td>
                                <td width="100">
                                    <input type="number" name="Quantity[]" placeholder="0" class="form-connect" required />
                                </td>
                                <td width="200">
                                    <input type="number" name="Price[]" placeholder="0.00" class="form-connect" id="prices"  disabled>
                                </td>
                            </tr>
                        </table>
                    </div>
                </div>

    </form>

<script>
        function myFunction(productID) {
                $.post(
                        'trial5.php',
                        {
                                product_id: productID
                        },
                        function (data) {
                                document.getElementById('prices').value = data;
                        }
                );
        }
    </script>

	The code for trial5.php
<?php
	include('config.php');
    $query = "SELECT Del_Price FROM tbl_product WHERE Product_ID=".$_POST['prodID'];
    $result = mysql_query($query)or die(mysql_error());
    $row = mysql_fetch_array($result);

    echo "$row[0]";
 ?>


	The code for append:

$(document).ready(function () {

                var newRow = $('#form-sample');
                var counter = 0;
                newRow.attr('id', counter);

                $("#clickbtn").click(function () {
                        $('#forms').append(newRow).html();

                        counter++;
                });
        });