How to show a message in the WordPress Admin

If you are working on a plugin or a theme, and you want to display some message to the user like "Settings have been saved" or "Plugin installed, Please goto settings page to configure it", then just follow the below snippet.

[php]
/**
* Generic function to show a message to the user using WP's
* standard CSS classes to make use of the already-defined
* message colour scheme.
*
* @param $message The message you want to tell the user.
* @param $errormsg If true, the message is an error, so use
* the red message style. If false, the message is a status
* message, so use the yellow information message style.
*/
function showMessage($message, $errormsg = false)
{
if ($errormsg) {
echo '<div id="message" class="error">';
}
else {
echo '<div id="message" class="updated fade">';
}

echo "<p><strong>$message</strong></p></div>";
}
[/php]
Now we just add a hook to the admin notices function to show our custom message.

[php]
/**
* Just show our message (with possible checking if we only want
* to show message to certain users.
*/
function showAdminMessages()
{
// Shows as an error message. You could add a link to the right page if you wanted.
showMessage("You need to upgrade your database as soon as possible...", true);

// Only show to admins
if (user_can('manage_options') {
showMessage("Hello admins!");
}
}

/**
* Call showAdminMessages() when showing other admin
* messages. The message only gets shown in the admin
* area, but not on the frontend of your WordPress site.
*/
add_action('admin_notices', 'showAdminMessages');[/php]

Done.....