<?php
class A { }

$a = new A;
$b = $a;  

$a->age = 10;
$b->age = 20;

echo $a->age; // ??????????

<?php

class A { 
  public int $age;
}

class B {
  public A $a;
}

$a = new A;
$b = new B;


$a->age = 0;
$b->a = $a;
$b->a->age = 5;
$a->age = 10;


echo $b->a->age; // ??????????

<?php

function tabe(A $a) {
  $a->age += 1;

  return null;
}

class A { 
  public int $age = 0;
}


$a = new A;

tabe($a);
tabe($a);

echo $a->age; // ???????????!!!!

class A
{ 
  public int $age = 0;
}

class B
{ 
  public A $a;

  public function __construct($a) {
    $this->a = $a
  }
}

$a = new A;
$b = new B($a);
$b->a->age = 13;

echo $a->age; // ????????????

class A
{ 
  public int $age = 0;
}

class B
{ 
  public A $a;

  public function __construct($a) {
    $this->a = $a
  }
}

$a = new A;

$b11 = new B($a);
$b22 = new B($a);

$b11->a->age = 11;
$b22->a->age = 22;

echo $b11->a->age; //????????

class A
{ 
  public int $age = 0;
}

class B
{ 
  public A $a;

  public function __construct($a) {
    $this->a = $a
  }
}

$a = new A;

$b11 = new B($a);
$b22 = clone $b11;

$b11->a->age = 11;
$b22->a->age = 22;

echo $b11->a->age; // ????????