How to make PHP session expire after X minutes

[MarPlo]

In "login.php" it is set a session ID for the logged user. Something simple:

Code: Select all

<?php
session_start();

// check login data received from a form ..

if($okdata === true) {
  $_SESSION['user_id'] = $uzer;
  header("Location: index.php");
}
else {
  echo 'Incorrect name or password';
}

In "index.php" I check if the $_SESSION['user_id'] exists, and display content according to user logged or not.

Code: Select all

<?php
session_start();
if(!isset($_SESSION['user_id'])) {
  echo 'User not logged';
}
else {
  echo 'User logged';
}

Now, how can I make the $_SESSION['user_id'] expire after 30 minutes?

Store a timestamp in the session.
In "login.php", register a session with the expired timestamp (when you want to expire that session) in the same time when the $_SESSION['user_id'] is created. Then, in "index.php" check if the current time exceds the expired timestamp.
Something like this:
"login.php - where the sessions are created

Code: Select all

<?php
session_start();

// check login data received from a form ..

if($okdata === true) {
  $_SESSION['expire'] = time() + 30 * 60;  // expire after 30 minutes
  $_SESSION['user_id'] = $uzer;
  header("Location: index.php");
}
else {
  echo 'Incorrect name or password';
}

index.php

Code: Select all

<?php
session_start();

// check if the sessions exist. If current time exceds $_SESSION['expire'], unset sessions
if(isset($_SESSION['expire']) && isset($_SESSION['user_id'])) {
  if(time() > $_SESSION['expire']) {
    unset($_SESSION['expire']);
    unset($_SESSION['user_id']);
  }
}

if(!isset($_SESSION['user_id'])) {
  echo 'User not logged';
}
else {
  echo 'User logged';
}