Implement Command Pattern for Complex Operations

interface CommandInterface
{
    public function execute();
}

class SendEmailCommand implements CommandInterface
{
    private $recipient;
    private $subject;
    private $body;

    public function __construct($recipient, $subject, $body)
    {
        $this->recipient = $recipient;
        $this->subject = $subject;
        $this->body = $body;
    }

    public function execute()
    {
        // Logic to send email
        echo "Sending email to {$this->recipient} with subject '{$this->subject}'";
    }
}

class CommandInvoker
{
    private $command;

    public function setCommand(CommandInterface $command)
    {
        $this->command = $command;
    }

    public function executeCommand()
    {
        $this->command->execute();
    }
}

// Usage
$invoker = new CommandInvoker();
$invoker->setCommand(new SendEmailCommand('user@example.com', 'Hello', 'This is a test email'));
$invoker->executeCommand();