Session missing after redirect (live server only) - php

Question

I have been created a login page for user to login. The code is working properly in localhost but not in live server. User can't login on live server and I found out that everytime redirect to index.php, the session will lost, so that user can't login due to lost of session. You have any idea on this?
<?php
session_start();
include "header.php";
if (!empty($_POST)){
include 'database_connect.php';
$username = $_POST['username'];
$password = $_POST['password'];
$username = stripslashes($username);
$password = stripslashes($password);
$username = mysql_real_escape_string($username);
$password = mysql_real_escape_string($password);
$sql = "SELECT * FROM users where username='$username' and password='$password'";
$result = mysql_query($sql, $con);
$rows = mysql_num_rows($result);
if ($rows == 1){
$_SESSION['username'] = $username;
echo "<script>window.location = \"index.php\";</script>";
//header("Location: index.php?" . SID);
}else{
echo "<div class='col-md-12 col-xs-8 alert alert-danger' align='center'>Invalid username and password. Please try again</div>";
}
mysql_close($con);
}
?>
Index.php
<? session_start();?>
<script>alert ('<?php echo $_SESSION['username']; ?>');</script>

Answer 1

Check session in your index.php page.just start session and echo user session. if you get then try if condition.
<?php session_start();
echo $_SESSION["username"];
if($_SESSION["username"]){
echo "bla bla";
}?>

Answer 2

<?php
session_start();
include "header.php";
if (!empty($_POST)){
include 'database_connect.php';
$username1 = $_POST['username']; // change it
$password1 = $_POST['password']; // change it
$username = stripslashes($username1); // change it
$password = stripslashes($password1); // change it
$username = mysql_real_escape_string($username);
$password = mysql_real_escape_string($password);
$sql = "SELECT * FROM users where username='$username' and password='$password'";
$result = mysql_query($sql, $con);
$rows = mysql_num_rows($result);
if ($rows == 1){
$_SESSION['username'] = $username;
echo "<script>window.location = \"index.php\";</script>";
//header("Location: index.php?" . SID);
}else{
echo "<div class='col-md-12 col-xs-8 alert alert-danger' align='center'>Invalid username and password. Please try again</div>";
}
mysql_close($con);
}
?>
You write same name username /password before strip the username/password as well as after , so change the name and try once

Answer 3

In the below code,
<?php session_start(); // your header.php file should not have a session start in that file
include "header.php";
if (!empty($_POST)){
include 'database_connect.php';
$username = $_POST['username'];
$password = $_POST['password'];
$username = stripslashes($username);
$password = stripslashes($password);
$username = mysql_real_escape_string($username);
$password = mysql_real_escape_string($password);
$sql = "SELECT * FROM users where username='$username' and password='$password'";
$result = mysql_query($sql, $con);
$rows = mysql_num_rows($result);
if ($rows == 1){
$_SESSION['username'] = $username;
?><script>alert ('<?php echo $_SESSION['username']; ?>');</script><?
echo "<script>window.location = \"index.php\";</script>";
exit();
//header("Location: index.php?" . SID);
}else{
echo "<div class='col-md-12 col-xs-8 alert alert-danger' align='center'>Invalid username and password. Please try again</div>";
}
mysql_close($con);
}
?>
You need to use session_start() function at the first line of the page after the php script starts