Four Ways to Show Message Bar After Redirecting to Another Page in PHP

There are four ways to show a message bar up front of the web page when needed in PHP. As shown below, the main function of the message bar is to notify users a warning message.

Four ways to build up a message bar are as follows:

1. Passing message by assigning a smarty variable.

index.php

<?php    
         :
$msg = 'Please login!';
         :
$smarty->assign('msg', $msg);    
// redirect to index.html
$smarty->display('index.html'); 
  
?> 

index.html

{if (isset($msg)}
  {$msg}
{/if}

It works very good except one situation: program redirects to another page and exits the original one before Smarty variable has been assigned.

Considering a situation below:

<?php
         :
if !login() {
  $msg = 'Please login!';
  header("location:login.php");
  exit;
}
         :
$smarty->assign('msg', $msg);    
// redirect to index.html
$smarty->display('index.html'); 
?>

Normally, we put $smarty->assign('msg', $msg); at the end of index.php file. It will not work in the above example since a header() command redirects to the login page and exits index.php. $msg will not be assigned to a Smarty variable.

2. Query string parameters

ex.
shopping_cart.html

<a href="index.php?msg=Cart is empty!">Empty Cart</a>  

index.php

$msg = isset($_REQUEST['msg']) ? 
  filter_var($_REQUEST['msg'], 
  FILTER_SANITIZE_MAGIC_QUOTES) : '';
echo $msg;

It shows a long line of words in the url windows of the browser. I really don’t like it. It is not a good way to do it.

3. Using Cookie

ex.
index.php

      :
setcookie('msg', 'Hello! New user!', time() + 365*86400);
      :
function show_message() {
  $msg = $_COOKIE['msg'];
  setcookie('msg', '', time() - 3600);
  return $msg;
} 

index.html

{if isset($smarty.cookies.msg)}
  {show_message()}
{/if}  

It seems to be a good solution, However, it resulted in some unexpected error while using cookie method. It was not stable when I tested it. The browser could not render the correct page. I recommend not to use it.

4. Using Session

ex.
index.php

<?php
session_start();
       :
       :
write_message('Hello! New user!');
header("location:{$_SERVER['HTTP_REFERER']}");
  
function write_message($msg = '') {
  $_SESSION['msg'] = $msg;
}

function show_message() {
  $msg = $_SESSION['msg'];
  unset($_SESSION['msg']);
  return $msg;
}
?> 

index.html

{if isset($smarty.session.msg)}
  <div class="alert alert-danger alert-dismissible show" role="alert">
    {show_message()}
    <button type="button" class="close" data-dismiss="alert" aria-label="Close">
      <span aria-hidden="true">&times;</span>
    </button>
  </div>
{/if} 

The session method is the most recommended method to show a message bar at the redirected page. It’s quite easy, simple and no restriction at all. You can insert write_message('xxxxx') anywhere in code and it will show up in the redirected page. The only one drawback to criticize is that it consumes server’s resources since session runs on the server.