Loader That assists with adding admin notices to a WordPress website.

composer require underpin/admin-notice-loader

This plugin uses a built-in autoloader, so as long as it is required before Underpin, it should work as-expected.

require_once(__DIR__ . '/underpin-admin-notices/admin-notices.php');

1. Install Underpin. See Underpin Docs
2. Register new admin notices as-needed.

A very basic example could look something like this. This example would always display a notice on the settings page.

\Underpin\underpin()->admin_notices()->add( 'example-notice', [
	'name'                    => 'Example notice',
	'description'             => 'This notice displays all the time.',
	'type'                    => 'notice',
	'is_dismissible'          => false,
	'wrapper_classes'         => [ 'class-1', 'class-2' ],
	'id'                      => 'example-notice',
	'message'                 => 'This will display all the time.',
	'should_display_callback' => '__return_true',
] );

This would display:

Alternatively, you can extend Admin_Notice and reference the extended class directly, like so:

underpin()->admin_notices()->add('key','Namespace\To\Class');