How to use the State design pattern in PHP for object behavior changes?

1
2
3

interface State {
    public function handle(): void;
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

class StateA implements State {
    private $context;
    
    public function __construct(Context $context) {
        $this->context = $context;
    }
    
    public function handle(): void {
        // do something
        $this->context->setState(new StateB($this->context));
    }
}

class StateB implements State {
    private $context;
    
    public function __construct(Context $context) {
        $this->context = $context;
    }
    
    public function handle(): void {
        // do something else
        $this->context->setState(new StateA($this->context));
    }
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15

class Context {
    private $state;
    
    public function __construct(State $state) {
        $this->state = $state;
    }
    
    public function setState(State $state): void {
        $this->state = $state;
    }
    
    public function handleRequest(): void {
        $this->state->handle();
    }
}

1
2
3
4
5

$context = new Context(new StateA($context));

// Call handleRequest multiple times to change the state and invoke the appropriate behavior
$context->handleRequest();
$context->handleRequest();