varia ble problem

when i  run the code below it not work but when I cahnge $Code02 to 12423 it work  But I try to check value of $Code02 by echo it get  12423


The code that not work

if($submit04)
{
echo $Code02 ;
include ("aut.inc");
$link_id1 = db_connect($default_dbname);

$sql = "UPDATE `sellhead`
                  SET `PayDate` ='$datedue01'

              WHERE Code= '$Code02' ";

$result = mysql_query($sql,$link_id1);
mysql_close($link_id1);


After I change  $Code02 to 12423  it can up date database

$sql = "UPDATE `sellhead`
                  SET `PayDate` ='$datedue01'

              WHERE Code= '12423 ' ";