login.php redirect to a blank page

Question

i have script login.php, it works when login with a true username and password, but when it comes login with wrong username and password it redirect to a blank page, when it should be redirect back to index.php here my script, may be some one can help me, what wrong with my script. thanks before.

<?php
session_start();
include 'dbconfig.php';


$username = mysql_real_escape_string($_POST['username']);
$password = mysql_real_escape_string($_POST['password']);


$username = stripslashes ($username);
$password = stripslashes ($password);

$query =  mysql_query("SELECT username, namalengkap, nik, level FROM users WHERE username= '$username' and password='$password'");

while($row = mysql_fetch_array($query)) {
$level= $row['level'];
$user = $row['namalengkap'];
$nik = $row['nik'];
if ($level == 'admin')
{

    $_SESSION['level'] = $level;
    $_SESSION ['user']= $user;
    $_SESSION ['nik'] = $nik;
    echo '<META HTTP-EQUIV="Refresh" Content="0; URL=homeadmin.php">';
exit;
}
elseif ($level == 'pengguna')
{
    $_SESSION['level'] = $level;
    $_SESSION ['user'] = $user;
    $_SESSION ['nik'] = $nik;
    echo '<META HTTP-EQUIV="Refresh" Content="0; URL=home.php">';
exit;
} 
else {
header("location:index.php");
}
 }
?>

Answer 1

Don't use mysql_query it has been depreciated Don't use while loop

 <?php
 session_start();
 include 'dbconfig.php';


 $username = mysql_real_escape_string($_POST['username']);
 $password = mysql_real_escape_string($_POST['password']);


 $username = stripslashes ($username);
 $password = stripslashes ($password);

 $query =  mysql_query("SELECT username, namalengkap, nik, level FROM users WHERE username= '$username' and password='$password'");

 $row = mysql_fetch_array($query);
 $level= $row['level'];
 $user = $row['namalengkap'];
 $nik = $row['nik'];
 if ($level == 'admin')
 {

 $_SESSION['level'] = $level;
 $_SESSION ['user']= $user;
 $_SESSION ['nik'] = $nik;

 header('Location:homeadmin.php');
 exit;
 }
 elseif ($level == 'pengguna')
 {
 $_SESSION['level'] = $level;
 $_SESSION ['user'] = $user;
 $_SESSION ['nik'] = $nik;
 header('Location:home.php');
 exit;
 } 
 else {
 header("location:index.php");
 }

 ?>