WordPress 5 Hello Word with translations commands

listing-18-15.php

<?php
/**
 * @package WH_Hello_World
 * @version 1.1.0
 */
/*
Plugin Name: WH Hello World
Plugin URI: https://wordpress-handbuch.com
Description: Testausgabe in Front- und Backend
Author: Johannes Mustermann
Version: 1.1.0
Author URI: https://ihredomain
*/

function hello_world_load_textdomain() {
	load_plugin_textdomain( 'wh-hello-world', false, basename( dirname( __FILE__ ) ) . '/languages' );
}

function hello_world() {
	echo "<script>alert('" . __('Hello World!', 'wh-hello-world') . "');</script>\n";
}

add_action( 'admin_head', 'hello_world' );
add_action( 'wp_head', 'hello_world' );
add_action( 'init', 'hello_world_load_textdomain' );