title: how to set session time out in php?
body: <pre><code>session_cache_expire( 20 );
  session_start(); // NEVER FORGET TO START THE SESSION!!!
  $inactive = 1200;
  if(isset($_SESSION['start']) ) {
      $session_life = time() - $_SESSION['start'];
      if($session_life &gt; $inactive){
          header("Location: user_logout.php");
      }
  }
  $_SESSION['start'] = time();
  if($_SESSION['valid_user'] != true){
  header('Location: ../index.php');
  }else{
  </code></pre>
  
  <p>I'm making an online examination system. I'm using PHP and MySQL.</p>
  
  <p>I want to set the session time, but don't know how. Please help me.</p>
  
  <p>Thanks in advance</p>