Add a notification to the admin top bar to show users if they are on the live / staging / test / dev version of a WordPress site

boswall-staging-notify.php

<?php

/*
Plugin Name: Site Environment Notification
Plugin URI: https://gist.github.com/boswall/c50836f73088ffc46fbd0922fd37e412
Description: Add a notification to the admin top bar to show users if they are on the ‘local’, ‘development’, ‘staging’ or ‘production’ version of the site. Use <code>define( 'WP_ENVIRONMENT_TYPE', 'local' );</code> to define this in the wp-config.php file.
Author: Matt Rose
Author URI: https://glaikit.co.uk/
*/

// If this file is called directly, abort.
if ( ! defined( 'WPINC' ) ) {
	die;
}

add_action( 'admin_bar_menu', 'boswall_staging_notify_admin_bar_node', 999 );
function boswall_staging_notify_admin_bar_node( $wp_admin_bar ) {
	if ( 'production' === wp_get_environment_type() ) {
		return;
	}
	$args = array(
		'id' => 'boswall-staging-notify',
		'title' => strtoupper( wp_get_environment_type() ),
		'meta' => array(
			'class' => wp_get_environment_type(),
		),
		'parent' => 'top-secondary',
	);

	$wp_admin_bar->add_node( $args );
	add_action( 'wp_after_admin_bar_render', 'boswall_staging_notify_admin_bar_styling' );
}

function boswall_staging_notify_admin_bar_styling() {
	?>
	<style media="screen">
		#wpadminbar ul li#wp-admin-bar-boswall-staging-notify {
			background-color: red;
		}
		#wpadminbar ul li#wp-admin-bar-boswall-staging-notify.development {
			background-color: darkmagenta;
		}
		#wpadminbar ul li#wp-admin-bar-boswall-staging-notify.local {
			background-color: darkgray;
		}
	</style>
	<?php
}