ralph03

Ok, finally I got the solution. The code is as below for sharing. Thanks guys for your help!
<?php
if (isset($_POST['update_btn'])){
   
    if (!empty($_POST['staffno'])) {
        $staffno = trim($_POST['staffno']);
    $appno = $_POST['appno']; // ID of the record to be updated
 
    $update = "UPDATE applicantabove18p2
                SET staffno = '$staffno'
                WHERE appid = '$appid'";
 
    $update1 = "UPDATE applicantabove18p1
                SET staffno = '$staffno'
                WHERE appid = '$appid'";
 
    $update2 = "UPDATE applicantabove18p1a
                SET staffno = '$staffno'
                WHERE appid = '$appid'";
 
    $update3 = "UPDATE applicantabove18att
                SET staffno = '$staffno'
                WHERE appno = '$appid'";
 
    if (mysqli_query($con, $update) && mysqli_query($con, $update1) && mysqli_query($con, $update2) && mysqli_query($con, $update3)) {
    if ($data){
 
        ?>
        <script type="text/javascript">
            alert("Data updated successfully");
            window.open("coordinatorview3.php","_self")
        </script>
        <?php
     }
    } else {
      echo "Update failed: " . mysqli_error($con);
    }
  } else {
    echo "Staff number cannot be empty";
 
}
}
 
?>