Add Flash Messages to Your Site

March 16, 2012

Flash messages are often used to give feedback to the user when an action has taken place. Such as, when they have logged in or tried to access a page without permission.

How it Works

Flash messages are set in $_SESSION['flash_messages']. At the beginning of every page request we store them in a variable and reset the $_SESSION. This gives us a chance to display the flash message, and prevents us from accidentally displaying it twice.

The Code

<?php
// make sure sessions work on the page
session_start();

class Flash {

  // where all messages are stored
  public static $messages = array();

  /*
   * A generic function to store flash messages
   *
   * Flash::add('notice', 'a message to display');
   *
   * @param string $name the name/id of the flash
   * @param string $message the message to display
   */
  public static function add($name, $message) {
    $_SESSION['flash_messages'][$name] = $message;
  }

  /*
   * A shortcut to Flash::add()
   *
   * Flash::notice('a message to display');
   */
  public static function __callStatic($fn, $args) {
    call_user_func_array(array('Flash', 'add'), array($fn, $args[0]));
  }
}

// if $_SESSION['flash_messages'] isset
// then save them to our class
if( isset($_SESSION['flash_messages']) ) {
  self::$messages = $_SESSION['flash_messages'];
}

// reset the session's value
$_SESSION['flash_messages'] = array();

The class’s job is to provide methods for us to add new messages. The work is done at the end where we store and reset the flash messages.

How to use the class

<?php

include 'flash.php';

// using Flash::add directly
Flash::add('notice', 'Awesome job dude!');

// using the alias
Flash::alert('lol, you can #39;t do that!');
// calls: Flash::add('alert', 'lol, you can #39;t do that!');

Displaying flash messages

<?php include 'flash.php'; ?>
...
<?php foreach( Flash::$messages as $id => $msg ) : ?>
  <div class="flash_<?php echo $id ?>"><?php echo $msg ?></div>
<?php endforeach; ?>

As you can see it is very easy to display the messages and you can have them implemented in no time at all.