<!-- Modal - Add Item -->
    <div class="modal fade" id="add_pitem" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
        <div class="modal-dialog" role="document">
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span></button>
                    <h4 class="modal-title" id="myModalLabel">Add New Item </h4>
                </div>
                <div class="modal-body">

    <?php
    $conn->close();
    $servername = "localhost"; $username = "root"; $password = ""; $db = "store";
    $conn = new mysqli($servername, $username, $password, $db);
    if ($conn->connect_error) { die("Connection failed: " . $conn->connect_error);}

    $res = mysqli_query($conn,"SHOW TABLES");
    echo "<div class='form-group'><label for='selectstore'>Select an store</label></div>";
    echo "<select name='selectstore' id='selectstore'>";
    while($row = mysqli_fetch_array($res))
    {
    echo "<option value='" . $row[0] . "'>" . $row[0] . "</option>"; }
    echo "<input type='hidden' name='table' value='$table'></select>";
    ?>
    <div class="form-group"><label for="pitem">Item</label>
    <select name="pitem" id="pitem"><option value="">Select Store first</option>
    <input type='hidden' name='table' value='<? echo '$table'; ?>'></select></div>
<div class="form-group"><label for="pquantity">Quantity</label>
    <input type="text" id="pquantity" placeholder="Select Item first" class="form-control"/></div>
    <div class="form-group"><label for="remarks">Remarks</label>
    <input type="text" id="remarks" placeholder="Remarks" class="form-control"/></div>
    <?php
    $conn->close();
    $server = "localhost";
    $username = "root";
    $password = "";
    $dbname = "project";
    $conn = new mysqli($server, $username, $password, $dbname);
    if ($conn->connect_error) {die("Connection failed: " . $conn->connect_error);}
    ?></div>
                <div class="modal-footer">
                    <button type="button" class="btn btn-default" data-dismiss="modal">Cancel</button>
                    <button type="button" class="btn btn-primary" onclick="add_pitem()">Add Item</button>
                </div>
            </div>
        </div>
    </div>
    <!-- // Modal -->

$(document).ready(function(){
    $('#selectstore').on('change',function(){
        var selectstore = $(this).val();
        if(selectstore){
            $.ajax({
                type:'POST',
                url:'loaditem.php',
                data:'selectstore='+selectstore,
                success:function(html){
                    $('#pitem').html(html);
                    $('#pquantity').html('<div class="form-group"><label for="quantity">Quantity</label><input type="text" id="quantity" placeholder="Select item first" class="form-control"/></div>');
                }
            });
        }else{
            $('#pitem').html('<option value="">Select Store first</option>');
            $('#pquantity').html('<div class="form-group"><label for="quantity">Quantity</label><input type="text" id="quantity" placeholder="Select item first" class="form-control"/></div>');
        }
    });

    $('#pitem').on('change',function(){
        var pitem = $(this).val();
        if(pitem){
            $.ajax({
                type:'POST',
                url:'loaditem.php',
                data:'pitem='+pitem,
                success:function(html){
                    $('#pquantity').html(html);
                }
            });
        }else{
            $('#pquantity').html('<div class="form-group"><label for="quantity">Quantity</label><input type="text" id="quantity" placeholder="Select item first" class="form-control"/></div>');
        }
    });
});

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "store";
$table = $_POST['table'];
$selectstore = $_POST['selectstore'];
$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);}

if(isset($_POST["selectstore"]) && !empty($_POST["selectstore"])){

$res = mysqli_query($conn,"SHOW TABLES");
echo "<div class='form-group'><label for='selectstore'>Select an store</label></div>";
echo "<select name='selectstore' id='selectstore'>";
while($row = mysqli_fetch_array($res))
{echo "<option value='" . $row[0] . "'>" . $row[0] . "</option>"; }
echo "<input type='hidden' name='table' value='$table'></select>";}

if(isset($_POST["pitem"]) && !empty($_POST["pitem"])){
     $query = $db->query("SELECT quantity FROM  `".$table."` WHERE item = `".$_POST['pitem']."` ");
     $rowCount = $query->num_rows;
    if($rowCount > 0){
   echo '<div class="form-group"><label for="pquantity">Quantity</label>';
        while($row = $query->fetch_assoc()){
   echo '<input type="text" id="pquantity" placeholder="available maximum quantity is '.$row['item'].'" class="form-control"/></div>';
        }
    }else{ echo '<div class="form-group"><label for="quantity">No Quantity Available</label></div>';
    }}
$conn->close();
?>