HelloCommand.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\Command;

/**
 * This concrete command calls "print" on the Receiver, but an external
 * invoker just knows that it can call "execute"
 */
class HelloCommand implements Command
{
    /**
     * Each concrete command is built with different receivers.
     * There can be one, many or completely no receivers, but there can be other commands in the parameters
     */
    public function __construct(private Receiver $output)
    {
    }

    /**
     * execute and output "Hello World".
     */
    public function execute()
    {
        // sometimes, there is no receiver and this is the command which does all the work
        $this->output->write('Hello World');
    }
}