<?php
    session_start();
    $db = @mysqli_connect("...", "...", "...") or
    die("Connection failed!");
    mysqli_select_db($db,'...');
    if(isset($_POST['username']))
    {
        $_SESSION['user'] = $_POST['username'];
        $_SESSION['password'] = md5($_POST['password']);
        $user = $_SESSION['user'];
        $password = $_SESSION['password'];
        $sql = "SELECT * FROM logins WHERE username = "$user"";
        $result = $db->query($sql);
        $row = $result->fetch_assoc();
        if($row["password"] == $password)
        {
            $_SESSION['logged'] = "loggedin";
        }
    }
?>

<?php
    session_start();
    session_destroy();
    unset($_SESSION['user']);
    unset($_SESSION['password']);
    header('Location: ../index.php');
?>

<?php
     if (isset($_SESSION['logged']))
     {
         $temp = $_SESSION["user"];
         echo "Hello $temp, nice to see you!";
     }
?>