title: Issue with PHP header function in Google Chrome
body: <p>After a successful login (i.e when user clicks the login button after entering the username and password), based on the user type I want to send user to a specific page. Below is my code. (Here, if usertype is 'employee', he should be taken to "data-update.php" page after clicking 'login' button.)</p>
  
  <p>This is the code in the index.php page:
      
  
  <pre><code>// This file is the home page.
  
  // Require the configuration before any PHP code as the configuration controls error reporting:
  require ('config.inc.php');
  
  // The config file also starts the session.
  
  // Require the database connection:
  require (MYSQL);
  
  // If it's a POST request, handle the login attempt:
  if ($_SERVER['REQUEST_METHOD'] == 'POST') {
      include ('login.inc.php');
  }
  
  /* PAGE CONTENT STARTS HERE! */
  ?&gt;
  &lt;!DOCTYPE html&gt;
  &lt;html lang="en"&gt;
  &lt;head&gt;
  ...
  </code></pre>
  
  <p>This is the code in the login.inc.php page:</p>
  
  <pre><code>&lt;?php 
  
  // This is the login page for the site.
  // It's included by index.php, which receives the login form data.
  
  // Array for recording errors:
  $login_errors = array();
  
  // Validate the username:
  
  
  // Validate the password:
  
  
  if (empty($login_errors)) { // OK to proceed!
  
  // Query the database:
  $q = "SELECT id, type FROM users WHERE (username='$u' AND pass='"  .  get_password_hash($p) .  "')";        
  $r = mysqli_query ($dbc, $q);
  
  if (mysqli_num_rows($r) == 1) { // A match was made.
  
      // Get the data:
      $row = mysqli_fetch_array ($r, MYSQLI_NUM); 
  
      // Store the data in a session:
      $_SESSION['user_id'] = $row[0];
      $_SESSION['username'] = $u;     
  
      if ($row[1] == 'employee') {
          reset_sms_update_session();
          header("Location: http://".BASE_URL."data-update.php");                         
          exit;
      }
      elseif ($row[1] == 'client'){
          header("Location: http://".BASE_URL."About.html");
          exit;
      }
  
  ...
  </code></pre>
  
  <p>And this is a partial code in "data-update.php" page:</p>
  
  <pre><code> // Start the session:
   session_start();
  
  function redirect_invalid_user($check = 'user_id', $destination = 'index.php', $protocol = 'http://') {
  
  // Check for the session item:
  if (!isset($_SESSION[$check])) {
      $url = $protocol . BASE_URL . $destination; // Define the URL.
      header("Location: $url");
      exit(); // Quit the script.
  }
  
  } // End of redirect_invalid_user() function.
  
  //Redirect to index.php if user not logged in
  redirect_invalid_user( );
  
  /* PAGE CONTENT STARTS HERE! */
  ?&gt;
  &lt;!DOCTYPE html&gt;
  
  ...
  </code></pre>
  
  <p>The problem is that, in Google Chrome when user clicks the login button, he is first taken to the index.php page (where the redirection occurs) and then he has to click login button again to be taken to "data-update.php" page.
  Why is this happening in Google Chrome?
  (FYI: this does not happen in XAMP testing environment in my local PC.)</p>
  
  <p>This does NOT happen in Firefox or IE8 (i.e. user is taken to "data-update.php" first time login button is clicked).</p>
  
  <p>Please help.</p>