CODESAMPLE

Command - PHP

Command PHP

The Command pattern encapsulates a request as an object, allowing parameterization of clients with different requests, queuing or logging of requests, and support for undoable operations. This implementation uses PHP interfaces to define the Command and Receiver roles. Concrete commands like LightOnCommand and LightOffCommand encapsulate the action and the receiver (a Light object). An Invoker (e.g., a RemoteControl) then executes the commands without knowing the underlying operation. This conforms to PHP’s object-oriented style by leveraging interfaces and classes for clear separation of concerns and extensibility.

<?php

/**
 * Receiver: Knows how to perform the action.
 */
class Light
{
    public function on()
    {
        echo "Light is on.\n";
    }

    public function off()
    {
        echo "Light is off.\n";
    }
}

/**
 * Command: Declares an interface for executing a request.
 */
interface Command
{
    public function execute();
    public function undo(); // Optional
}

/**
 * Concrete Command: Binds a receiver to an action.
 */
class LightOnCommand implements Command
{
    private Light $light;

    public function __construct(Light $light)
    {
        $this->light = $light;
    }

    public function execute()
    {
        $this->light->on();
    }

    public function undo()
    {
        $this->light->off();
    }
}

/**
 * Concrete Command: Binds a receiver to an action.
 */
class LightOffCommand implements Command
{
    private Light $light;

    public function __construct(Light $light)
    {
        $this->light = $light;
    }

    public function execute()
    {
        $this->light->off();
    }

    public function undo()
    {
        $this->light->on();
    }
}


/**
 * Invoker: Requests the command to execute.
 */
class RemoteControl
{
    private Command $command;

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

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

// Client code
$light = new Light();
$onCommand = new LightOnCommand($light);
$offCommand = new LightOffCommand($light);

$remote = new RemoteControl();
$remote->setCommand($onCommand);
$remote->buttonPressed();

$remote->setCommand($offCommand);
$remote->buttonPressed();

?>