Creating an object inside another class?

Question

PHP

Question 1 - is the following option correct, if not, why not?

class A {
}

class B {
  public $a;

  function __construct() {
    $this->a = new A();
  }
}

2. Even if it's not exactly a true option, it works for me. Question 2. Why is it possible to write an object of another class to a property only through a constructor? It doesn't work like that, but PHP syntax seems to make sense.

class A {
}

class B {
  public $a = new A();
}

upd. It would be very interesting to know the opinion of those who looked at the PHP source code. Maybe this approach really carries hidden logic.

Answer 1

It doesn't work like that, but PHP syntax seems to make sense.

for

This declaration may include an initialization, but this initialization must be a constant value--that is, it must be able to be evaluated at compile time and must not depend on run-time information in order to be evaluated.

agree or not - it's up to you. in real life it won't change anything.