3.5. Memento¶

 1<?php
 2
 3// Originator class
 4class Editor
 5{
 6    private string $content;
 7
 8    public function __construct()
 9    {
10        $this->content = '';
11    }
12
13    public function type(string $words): void
14    {
15        $this->content .= ' ' . $words;
16    }
17
18    public function getContent(): string
19    {
20        return $this->content;
21    }
22
23    public function save(): EditorMemento
24    {
25        return new EditorMemento($this->content);
26    }
27
28    public function restore(EditorMemento $memento): void
29    {
30        $this->content = $memento->getContent();
31    }
32}

 1<?php
 2
 3// Memento class
 4class EditorMemento
 5{
 6    private string $content;
 7
 8    public function __construct(string $content)
 9    {
10        $this->content = $content;
11    }
12
13    public function getContent(): string
14    {
15        return $this->content;
16    }
17}

 1<?php
 2
 3// Caretaker class
 4class EditorHistory
 5{
 6    private array $mementos = [];
 7
 8    public function addMemento(EditorMemento $memento): void
 9    {
10        $this->mementos[] = $memento;
11    }
12
13    public function getMemento(int $index): EditorMemento
14    {
15        return $this->mementos[$index];
16    }
17}

 1<?php
 2
 3// Usage example
 4$editor = new Editor();
 5$editor->type('This is the first sentence.');
 6$editor->type('This is the second sentence.');
 7
 8// Save the current state
 9$history = new EditorHistory();
10$history->addMemento($editor->save());
11
12// Add more content
13$editor->type('This is the third sentence.');
14
15// Restore to previous state
16$editor->restore($history->getMemento(0));
17
18echo $editor->getContent(); // Output: This is the first sentence. This is the second sentence.