How can I send user session from one page to another till destroyed in php and mysql

Question

I have session page with these code

session_start();

if (!isset($_SESSION['id'])){
header('location:order.php');
}

$ses_id = $_SESSION['id'];

I included it into my login page (order.php)

<?php include('session.php'); ?>

Here is the login scripts and functions

$username = clean($_POST['username']);
$password =  md5($_POST['password']);
$apollos=$username;
$query=Login($username,$password);
$count = mysql_num_rows($query);
$row = mysql_fetch_array($query);
$phone=$row['Contact_Number'];

DeleteActivation($username);

if ($count > 0) {
    $_SESSION['id'] = $row['memberID'];

    UserPin($username,$pin,$member);
    $From='eFarms';
    $Message='Your User Login Pin from St. Apollos eFarms is '.$pin;

    die("<script>location.href = 'login_sms.php'</script>");
    session_write_close();
} else {
    session_write_close();
}

Here is my Pin Validation Page

<?php include('header.php'); ?>
pin = clean($_POST['pin']);


$query=CheckPin($username,$pin,$member);

$count = mysql_num_rows($query);
$row = mysql_fetch_array($query)

if ($count > 0) {
    $_SESSION['id'] = $row['memberID'];
    die("<script>location.href = 'user_home.php'</script>");
    session_write_close();
} else {
    session_write_close();
}

Someone should please examine these codes, correct and show me how to receive the session to the USer Home Page as Username.

Answer 1

Before session start you have to check the session is already started or not like below in each script or in common script file.

if (!isset($_SESSION)) {
    session_start();
}

Edited:

the above condition is not needed as it is checking internally as descripe in the documentation - http://php.net/manual/en/function.session-start.php

session_start();

Answer 2

First, as provided by others, ur using very bad and insecure method ! Try to use PDO which is much easier (when u understand how it work) and it's much more secure !

Second, ur coding is not so clean, I think that's why u can't find the problem urself !

And finally, I think ur missing :

session_start();

in some part of ur code !