Warning: Invalid argument supplied for foreach() ช่วยทีค่ะ

<?php
include("include/header.php");
include("include/left_menu.php");
?>
<!-- Content Wrapper. Contains page content -->

<div class="content-wrapper"> 
  <!-- Content Header (Page header) -->
  <section class="content-header">
    <h1> จัดทําใบส่งสินค้า <small>( Delivery Order )</small> </h1>
    <ol class="breadcrumb">
      <li><a href="index.php"><i class="fa fa-home"></i> หน้าแรก</a></li>
      <li class="active">จัดทําใบส่งสินค้า</li>
    </ol>
  </section>
  
  <!-- Main content -->
  <section class="content"> 
    <!-- Main row -->
    <div class="row"> 
      <!-- /.box -->
      <div class="col-md-12"> 
        <!-- Horizontal Form -->
        <div class="box box-info"> 
          <!-- /.box-header --> 
          <!-- form start -->
          <table class="table table-bordered">
            <tr>
              <th>รหัสสั่งซื้อ</th>
              <th>ชื่อ - นามสกุล</th>
              <th>วันเวลาที่สั่ง</th>
              <th>จำนวน</th>
              <th>ราคารวม</th>
              <th>&nbsp;</th>
            </tr>
            <?php
			$sql = "SELECT sell.*,custommer.* FROM sell LEFT JOIN custommer ON (sell.cus_id = custommer.cus_id) WHERE sell.status = '5' ORDER BY sell.sell_id DESC";
			$db->free_array();
			$db->query($sql);
			foreach ($db->fetch_array() as $row)
			{
				$sql = "SELECT SUM(num) as total FROM `sell_detail` WHERE sell_id = '".$row['sell_id']."'";
				$db->free_array();
				$db->query($sql);
				$data = $db->fetch_array();
				echo '
				<tr>
					<td>'.$row['order_id'].'</td>
					<td>'.$row['fname'].' '.$row['lname'].'</td>
					<td>'.DateThai($row['sell_date']).'</td>
					<td align="right">'.$data[0]['total'].'</td>
					<td align="right">'.number_format($row['total_price'],2).'</td>
					<td><a data-toggle="modal" data-backdrop="static" class="btn btn-xs btn-success" href="user_send_print_behind.php?order_id='.$row['order_id'].'" data-target="#myModal">พิมพ์ใบส่งสินค้า</a> <button type="button" class="btn btn-xs btn-primary confirm-order" id="'.$row['order_id'].'">ยืนยันการพิมพ์ใบส่งสินค้า</button>
					</td>
				</tr>';
			}
			?>
          </table>
        </div>
      </div>
    </div>
    <!-- /.row (main row) --> 
    
  </section>
  <!-- /.content --> 
</div>
<!-- /.content-wrapper --> 

<!-- Modal -->
<div class="modal fade bs-example-modal-lg" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
    <div class="modal-dialog modal-lg">
        <div class="modal-content">
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
                 <h4 class="modal-title">รายการส่งสินค้า</h4>

            </div>
            <div class="modal-body"></div>
            <div class="modal-footer">
                <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
            </div>
        </div>
        <!-- /.modal-content -->
    </div>
    <!-- /.modal-dialog -->
</div>
<?php include("include/footer.php");?>
<?php include("include/js.php");?>
<script language="javascript">
$(document).ready(function() {
	$('.order_detail').live('click',function() {
		var order_id = $(this).attr('id');
		$.post("user_send_print_behind.php", {
			get_order_detail : 1,
			order_id : order_id},
			function(data) {
				$('#show_order_detail').html(data);
				$('#myModal-order-id').modal('show');
		});
	});
	$('.confirm-order').live('click',function() {
		var order_id = $(this).attr('id');
		if (confirm("ต้องการยืนยันการพิมพ์ใบส่งสินค้า ใช่หรือไม่?"))
		{
			$.post("user_send_print_behind.php", {
				print_confirm : 1,
				order_id : order_id},
				function(data) {
					window.location="user_send_print.php";
			});
		}
	});
	$('#print').live('click',function() {
		printpage('pirnt_detail');
	});
});
</script>
</body></html>