<form class="form-horizontal" method="post" action="" id="order_form">
    <fieldset class="orders_det">
        <div class="form-group">
            <label for="prod_type">Type</label>
            <select name="prod_type[]" class="form-control prod">
                <option value="">-- Select Products --</option>
                <option value="prod1">Prod1</option>
                <option value="prod2">Prod2</option>
                <option value="prod3">Prod3</option>
            </select>
        </div>
        <div class="form-group">
            <label for="quant" class="control-label col-md-2" >Quantity</label>
            <div class="form-control col-md-6">
              <input type="text" class="form-control quant" name="quant[]">
            </div>
            <div>
                <button type="button" class="btn btn-success" id="more_btn">Add More Orders + </button>
            </div>
        </div>
        <div class="more_orders">
        </div>
    </fieldset>
    <div class="form-group">
        <label for="name" class="col-md-2 control-label">Name</label>
        <div class="col-md-8">
            <input type="text" class="form-control name" name="name">
        </div>
    </div>
    <div class="form-group">
        <button type="submit" class="btn btn-success" name="order_submit" id="order_submit">Submit Order</button>

$(document).ready(function() {
      $('form button#more_btn').on("click", function(e) {//to generate dynamic fields
        e.preventDefault();
        var moreOrders = '';
              moreOrders += '<div class="new_order">';
              moreOrders += '<div class="form-group">';
              moreOrders += '<label for="prod_type">Type</label>';
              moreOrders += '<select name="prod_type[]" class="form-control prod">';
              moreOrders += '<option value="">-- Select Products --</option>';
              moreOrders += '<option value="prod1">Prod1</option>';
              moreOrders += '<option value="prod2">Prod2</option>';
              moreOrders += '<option value="prod3">Prod3</option>';
              moreOrders += '</select>';
              moreOrders += '</div> ';
              moreOrders += '<div class="form-group">';
              moreOrders += '<label for="quant" class="control-label col-md-2" >Quantity</label>';
              moreOrders += '<div class="form-control col-md-6">';
              moreOrders += '<input type="text" class="form-control quant" name="quant[]">';
              moreOrders += '</div>';
              moreOrders += '<div>';
              moreOrders += '</div><br />';
              $('.more_orders').append(moreOrders);
      });

      $("form").on("change", function(e) {//to generate a preview table
        var prod = $("form select[name='prod_type[]']");
        var quant = $("form input[name='quant[]']");
        var table = '';
              table += '<table>';
              table += '<thead>';
              table += '<tr>';
              table += '<th>Product</th>';
              table += '<th>Quantity</th>';
              table += '<th>Cost</th>';
              table += '</tr>';
              table += '</thead>';
              table += '<tbody>';
              table += '<tr>';
            prod.each(function(i) {
                $.post('fetch_cost.php', {'type':$(this).val()}, function(cost){
                  table += '<tr>';
                  table += '<td>' + $(this).val() + '</td>';
                  table += '<td>' + quant.eq(i).val() + '</td>';
                  table += '<td>' + cost + '</td>';
                  table += '</tr>';
                 });
                });
              table += '</tr>';
              table += '</tbody>';
              table += '</table>';
              $(".orders_preview").html(table);
            });
    });

<?php
      require("conn.php");
      $type = $_POST['type'];
      $sql = mysqli_query($conn, "SELECT cost from product_cost WHERE product ='$type'");
            if ($sql){
                  while ($row = mysqli_fetch_row($sql)){
                        $cost = $row[0];
                        echo $cost;
                  }
            }
?>