ปัญหาในการเลือกลบข้อมูลด้วย checkbox ไม่ได้ ช่วยตรวจสอบให้ทีครับผม

<form id="form1" name="form1" method="post" action="../php_pro/delpoll_admin.php">
 <table width="100%" border="0" cellspacing="0" cellpadding="0">
  <tr>
    <td colspan="3" align="center"><label>
      <input type="submit" name="button" id="button" value="ลบข้อมูล" />
    </label></td>
    </tr>
  <tr>
    <td width="5%" align="center"><strong>ลำดับ</strong></td>
    <td width="16%" align="center"><strong>Username</strong></td>
    <td width="9%" align="center"><strong>ลบโพย</strong></td>
    </tr>
  <?
$sql = "select * from tb_poll as p,tb_customer as c
				where		c.cus_id= p.cus_id
				and		p.poll_sta = '2'
				order by p.poll_date";
		$res = mysql_db_query($db,$sql);
		while($record = mysql_fetch_array($res)){
	$bgcolor =($i++%2)?'#EAEFF7':'#fafafa';
  ?>
  <tr>
    <td align="center" bgcolor="<?=$bgcolor?>"><?=$i?></td>
    <td align="center" bgcolor="<?=$bgcolor?>"><?=$record[cus_user]?></td>
    <td align="center" bgcolor="<?=$bgcolor?>">
      <label>
        <input name="poll_del[]" type="checkbox" id="poll_del" value="<?= $record[poll_id]?>" />
      </label>
    </td>
    </tr>
  <? } ?>
</table>
<input name="num" type="hidden" value="<?=$i?>" />
</form>

for($i=0;$i<count($_POST['poll_del']);$i++){
	if(trim($_POST['poll_del'][$i]) != ""){
	$poll_id[$i]=trim($_POST['poll_del'][$i])."<br>";
		$sql1 = "delete from tb_poll  where  poll_id='$poll_id'";
		$result1 = mysql_db_query($db,$sql1)or die(mysql_error());
		echo $sql1."<br>";
		$sql2 = "delete from tb_poll_dt  where  poll_id='$poll_id'";
		$result2 = mysql_db_query($db,$sql2)or die(mysql_error());
		echo $sql2."<br>";
		$sql3 = "delete from tb_poll_sum  where  poll_id='$poll_id'";
		$result3 = mysql_db_query($db,$sql3)or die(mysql_error());
		echo $sql3."<hr>";
	   }
	}