How to update values in table - php

Question

I cannot update the values in my table with this code, if the update is successful the page should redirect in ('Location:ui.php'), how can this be achieved?
<?php
ob_start();
include('dbconnect.php');
$code=$_GET['stallcode'];
if(isset($_POST['submit']))
{
$pcost = $_POST['pcost'];
$tcost = $_POST['tcost'];
$cash = $_POST['cash'];
$change = $_POST['change'];
if (($cash == '0'))
{
$pstatus="0";
}
else
{
$pstatus="1";
}
$updated=mysql_query("UPDATE tbl_stallowner SET
paymentstatus='$pstatus', penaltycost='$pcost', totalcost='$tcost', cash='$cash', change='$change'
WHERE stallcode='$code'")or die();
if($updated)
{
$msg="Successfully Updated!!";
header('Location:ui.php');
}
} //update ends here
ob_end_flush();
?>

Answer 1

As you redirects users by checking if($updated) is true, this will not work, you should check the number of affected rows instead using mysql_num_rows.
Also remember to exit; after header() to stop the execution.
$num_rows = mysql_num_rows($updated);
if($num_rows > 0)
{
$msg="Successfully Updated!!";
header('Location:ui.php');
exit;
}
Tip: You should not be using MySQL as it has already been deprecated, use MySQLi instead.

Answer 2

You want to use mysqli, not it's predecessor, mysql. Mysql is vulnerable and open to exploitation, here's what you should write in each of your files:
dbconnect.php
<?php
$conn = mysqli_connect("localhost","my_user","my_password","my_db");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
?>
updatestallowner.php (or whatever you named it)
<?php
ob_start();
require('dbconnect.php');
$code = mysqli_real_escape_string($conn, $_GET['stallcode']);
if(isset($_POST['submit'])){
$pcost = mysqli_real_escape_string($conn, $_POST['pcost']);
$tcost = mysqli_real_escape_string($conn, $_POST['tcost']);
$cash = mysqli_real_escape_string($conn, $_POST['cash']);
$change = mysqli_real_escape_string($conn, $_POST['change']);
if ($cash == '0') {
$pstatus="0";
} else{
$pstatus="1";
}
$sql = "UPDATE tbl_stallowner SET paymentstatus='$pstatus', penaltycost='$pcost', totalcost='$tcost', cash='$cash', change='$change' WHERE stallcode='$code';";
$result = mysqli_query($conn, $sql);
if($result) {
$msg="Successfully Updated!!";
header('Location: ui.php');
exit;
} else {
die("Error updating!");
}
}
?>
Good luck!