ตรวจสอบ Checkbox ด้วย for แล้วค่าไม่มาครับ คือผมทำ checkbox ไว้หลายอัน แล้วให้ตรวจสอบด้วย for แต่ค่าไม่มาครับ

<?

$checkidbring = $_POST["checkidbring"];
echo "count = ".count($checkidbring)."<br>";
for($i=0; $i <count($checkidbring); $i++)
{

$number=$_POST["number".$checkidbring[$i]];echo"$number";
$_SESSION["number".$checkidbring[$i]] = $number;
//echo " $_SESSION[\"number\"".$chkcsmaterialID[$i]."] = $number";
echo "checkidbring $i = ".$checkidbring[$i]."<br>";

include "connect.php";

$result=mysql_db_query($dbname,$sql);
$sql="SELECT * FROM tb_bring WHERE idbring='$checkidbring[$i]'" ;
echo "$sql";



$temp =(int)$amount-(int)$number ;

$amountwant= $checkidbring[$i];
echo "$amountwant";

if($temp>=0)
{

$sql1 = "update tb_bring set amount='$temp' where idbring='$amountwant' ";
echo "$sql1<br>";
$result1 = mysql_query($sql1);

$sql2= "INSERT INTO tb_bringwant (checkidbring, amountwant)
VALUES('$idbring[$i]','$temp')";
echo "$sql2 <br>";
$result2 = mysql_query($sql2);
}
}


session_register("checkidbring");

?>

<?php if (empty($_POST)){ ?>


<form id="form1" name="form1" method="post" action="">
  <p>
    <input name="chk[]" type="checkbox" id="chk[]" value="1" />
  1</p>
  <p>
    <input name="chk[]" type="checkbox" id="chk[]" value="2" />
    2</p>
  <p>
    <input name="chk[]" type="checkbox" id="chk[]" value="3" />
  3</p>
  <p>
    <input name="chk[]" type="checkbox" id="chk[]" value="4" />
  4</p>
  <p>
    <input name="chk[]" type="checkbox" id="chk[]" value="5" />
    5
  </p>
  <p>
    <input type="submit" name="button" id="button" value="Submit" />
  </p>
</form>
<?php } else { ?>

<?php 

$txt = $_POST['chk'];

for($i = 0; $i<count($txt); $i++):

echo $txt[$i];

endfor;

?>

<?php } ?>