nodes-visitors-1.php

<?php

abstract class Node {}

class Calculator extends Node {
    public function __construct(public array $statements){}
}

class Add extends Node {
    public function __construct(public Node $left, public Node $right){}
}

class Substract extends Node {
    public function __construct(public Node $left, public Node $right){}
}

class Minus extends Node {
    public function __construct(public Node $node){}
}

class Number extends Node {
    public function __construct(public float $value){}
}

class Assign extends Node {
    public function __construct(public string $variable, public Node $node){}
}

class Get extends Node {
    public function __construct(public string $variable){}
}

$firstStatement = new Assign('foo', new Add(new Number(1), new Number(5)));
$secondStatement = new Substract(new Number(100), new Minus(new Get('foo')));
$calculator = new Calculator([$firstStatement, $secondStatement]);

var_dump($calculator);