3.2. Command¶

1<?php
2
3// Command interface
4interface Command
5{
6    public function execute();
7
8    public function undo();
9}

 1<?php
 2
 3// Concrete command class for adding numbers
 4class AddCommand implements Command
 5{
 6    private Receiver $receiver;
 7    private int $value;
 8
 9    public function __construct(Receiver $receiver, int $value)
10    {
11        $this->receiver = $receiver;
12        $this->value = $value;
13    }
14
15    public function execute()
16    {
17        $this->receiver->add($this->value);
18    }
19
20    public function undo()
21    {
22        $this->receiver->subtract($this->value);
23    }
24}
25
26// Concrete command class for subtracting numbers
27class SubtractCommand implements Command
28{
29    private Receiver $receiver;
30    private int $value;
31
32    public function __construct(Receiver $receiver, int $value)
33    {
34        $this->receiver = $receiver;
35        $this->value = $value;
36    }
37
38    public function execute()
39    {
40        $this->receiver->subtract($this->value);
41    }
42
43    public function undo()
44    {
45        $this->receiver->add($this->value);
46    }
47}

 1<?php
 2
 3// Receiver class that performs the operations
 4class Receiver
 5{
 6    private int $value = 0;
 7
 8    public function add($value): void
 9    {
10        $this->value += $value;
11    }
12
13    public function subtract($value): void
14    {
15        $this->value -= $value;
16    }
17
18    public function getValue(): int
19    {
20        return $this->value;
21    }
22}

 1<?php
 2
 3// Invoker class that manages the commands
 4class Invoker
 5{
 6    private array $commands = [];
 7    private array $undoStack = [];
 8
 9    public function addCommand(Command $command): void
10    {
11        $this->commands[] = $command;
12    }
13
14    public function executeCommands(): void
15    {
16        foreach ($this->commands as $command) {
17            $command->execute();
18            $this->undoStack[] = $command;
19        }
20        $this->commands = [];
21    }
22
23    public function undo(): void
24    {
25        if (!empty($this->undoStack)) {
26            $command = array_pop($this->undoStack);
27            $command->undo();
28        }
29    }
30}

 1<?php
 2
 3// Client code
 4$receiver = new Receiver();
 5$invoker = new Invoker();
 6
 7$invoker->addCommand(new AddCommand($receiver, 5));
 8$invoker->addCommand(new SubtractCommand($receiver, 3));
 9$invoker->executeCommands();
10
11echo "Current value: " . $receiver->getValue() . "\n"; // Output: Current value: 2
12
13$invoker->undo();
14echo "Undone: Current value: " . $receiver->getValue() . "\n"; // Output: Undone: Current value: 5