PHP Login stay logged in (Session)

Question

In the following PHP code, I want to include a function, setting a cookie to stay logged in. The problem is, that samples I found on google aren't working. The users should get a cookie if they have signed in, without an additional "stay logged in" button. In every new request, the cookie should log in the user immediately.

    <?php
// Initialize the session
session_start();

// Check if the user is already logged in, if yes then redirect him to welcome page
if(isset($_SESSION["loggedin"]) && $_SESSION["loggedin"] === true){
  header("location: index.php");
  exit;
}



// Include config file
require_once "configuser.php";

// Define variables and initialize with empty values
$username = $password = "";
$username_err = $password_err = "";

// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){

    // Check if username is empty
    if(empty(trim($_POST["username"]))){
        $username_err = "Bitte Benutzernamen eingeben.";
    } else{
        $username = trim($_POST["username"]);
    }

    // Check if password is empty
    if(empty(trim($_POST["password"]))){
        $password_err = "Bitte Passwort eingeben.";
    } else{
        $password = trim($_POST["password"]);
    }

    // Validate credentials
    if(empty($username_err) && empty($password_err)){
        // Prepare a select statement
        $sql = "SELECT id, username, password FROM users WHERE username = ?";

        if($stmt = mysqli_prepare($link, $sql)){
            // Bind variables to the prepared statement as parameters
            mysqli_stmt_bind_param($stmt, "s", $param_username);

            // Set parameters
            $param_username = $username;

            // Attempt to execute the prepared statement
            if(mysqli_stmt_execute($stmt)){
                // Store result
                mysqli_stmt_store_result($stmt);

                // Check if username exists, if yes then verify password
                if(mysqli_stmt_num_rows($stmt) == 1){                    
                    // Bind result variables
                    mysqli_stmt_bind_result($stmt, $id, $username, $hashed_password);
                    if(mysqli_stmt_fetch($stmt)){
                        if(password_verify($password, $hashed_password)){
                            // Password is correct, so start a new session
                            session_start();

                            // Store data in session variables
                            $_SESSION["loggedin"] = true;
                            $_SESSION["id"] = $id;
                            $_SESSION["username"] = $username;

                            //Angemeldet bleiben:

                            // Redirect user to welcome page
                            header("location: index.php");
                        } else{
                            // Display an error message if password is not valid
                            $password_err = "Passwort falsch.";
                        }
                    }
                } else{
                    // Display an error message if username doesn't exist
                    $username_err = "Benutzername oder Passwort falsch.";
                }
            } else{
                echo "Störung.";
            }
        }

        // Close statement
        mysqli_stmt_close($stmt);
    }

    // Close connection
    mysqli_close($link);
}
?>

<!DOCTYPE html>

What is the problem now: Isn't the user redirected to login.php? Can't you login the user at all? ..? Describe what is happening now when a user logs in. Or _is_ everything up and running and you just want to add a Cookie? — Jeff, Nov 11 '18 at 11:17

Amir · Answer 1 · 2018-11-12T06:02:04.967

Set the cookie after you verifying the password :

if(password_verify($password, $hashed_password)) {
    // Password is correct, so start a new session
    session_start();

    // store user data in cookie
    setcookie('user', json_encode([
        'username' => $username,
        'password' => $password
    ]), time() + 3600 * 24 * 30);

Then before checking loggedin variable in the session, check for the cookie(please pay attention closely to the commented lines here):

// Check if there is an already logged in user in the cookie and then set its data to the session
if(isset($_COOKIE['user']) && !isset($_SESSION["loggedin"])) {
    $user = json_decode($_COOKIE['user'], true);

    // do the stuff to check if there is a user with $user['username'] and $user['password'] in the database, then if there is one, do as below :
    $_SESSION["loggedin"] = true;
    $_SESSION["id"] = $userId; // retrieved from database
    $_SESSION["username"] = $user['username'];
    // else if there is no user with that credentials from cookie, do the following to prevent further checking on database :
    $_SESSION["loggedin"] = false;

}

// Check if the user is already logged in, if yes then redirect him to welcome page
if(isset($_SESSION["loggedin"]) && $_SESSION["loggedin"] === true){

In order to destroy the cookie when you're logging out the user, use unset as already @DakshMehta said about this:

unset($_COOKIE['user']);

caution: It's not recommended to store user's password in the cookie due to security issues. So maybe you want to implement a token based authentication which refreshes the token after a short period of time or at least on each login. Using json web tokens(jwt) could be helpful on this topic and there is this package that implements jwt in php : firebase/php-jwt You should be aware that a token is acting exactly like a password, so when you store it in the cookie, you should consider some security tips which is mentioned here in the last section of this article : Where to Store your JWTs – Cookies vs HTML5 Web Storage

__caution:__ I could now set a cookie in my browser and would be logged in as any user I want to! — Jeff, Nov 11 '18 at 12:10
Use authentication tokens, not user ids for cookies. related read: https://stackoverflow.com/questions/1592534/what-is-token-based-authentication — Jeff, Nov 11 '18 at 12:22
In order to unset the cookie, you can just use the unset on $_COOKIE variable. Have a look at the https://secure.php.net/manual/en/function.unset.php — Daksh Mehta, Nov 11 '18 at 15:50
@Jeff thanks for the tip. you're absolutely right. I just wanted to write a quick answer and didn't pay attention closely to the situation, sorry. How about we store the username and password in the cookie, and then if already there is no `loggedin` session, we check if password from cookie is correct according to the database. Then if the password is correct we set the session. I updated my answer so you can check on what I'm saying. — Amir, Nov 11 '18 at 17:51
_"password from cookie"_ - no, __never ever__ store the user's password in a cookie. Not even a hash. In no case ever. Store an auth token that get's refreshed minimum on each login. — Jeff, Nov 11 '18 at 19:26

PHP Login stay logged in (Session)

1 Answers1