PHP FOR SQL RELATED LOGINS.

<?php
session_start();
$username = $_POST["username"];
$password=$_POST["password"];
if ($username=="John" && $password=="pass"){
 $_SESSION['login']= $username;
 header("location: index.php");
}
else{
 header("location: login.html");
}
?>

PHP HEADER FOR ANY PAGE THAT REQUIRES A LOGGED IN USER

<?php
session_start();
if (!isset($_SESSION['login'])) {
 header("location: login.html");
}
else{
 print "You've successfully logged in.<br>";
 session_destroy( ); // simulation of logout
}
?>

USER LOGIN FORM VALIDATION

<?php
session_start();
if(!empty($_POST["username"])) // if username not empty
 {
 $username = $_POST["username"];
 $password = $_POST["password"];
 if($username == "user1") { // Simulation of
database login query for $username
 if($password == "pass1") { // Simulation
of database login query for $password

 $_SESSION['login'] = $username;
 echo 4; // Success!
 }
 else echo 3; // username OK but password
incorrect
 }
 else echo 2; //username incorrect
}
else echo 1; // usernameis blank

?>

FOR THE LOGOUT.PHP

<?php
session_start();
session_destroy();
echo "You have logged out! If your browser does not redirect you, click the link below!<br><br>";
// sleep for 4 seconds
sleep(4)
header( 'Location: /index.html' );
// Shannon, honestly dunno if that redirect to index works,
// but, whatever its worth a shot for some marks.
?>