In PHP, static variables are bound to a specific method -- if the method is inherited, then it also gets separate static variables. This means that C::__construct() has static variables independent of A::__construct().

I'm going to close this as a duplicate of bug #74198, because the behavior of static variables in methods and their interaction with inheritance is currently not documented.

Hi, 

what i dont get is the different behavior of the twice call
$c = new C;
$c->__construct();

the first line calles A::__construct and shows 5
the second lines calls then the method with a separate static and shows 1

So this statement is not valid here:
"if the method is inherited, then it also gets separate static variables"

If this statement is right, then the two calls have to have 1 and 2 as result, no 5 and 1, or?

Normaly u dont call $c->__construct() on an existing object, 
but why is direct call of __construct so different?

But thanks, for the reply.

Oh, I missed that "new C" and "$c->__construct()" produce different results. Agree that this doesn't seem right.

I have tested in another way

class A {
 public function test(){
    static $test  = 0;
    print (++$test);
 }
 public function __construct(){
    $this->test();
 }
}
class B extends A {
    public function __construct(){
        parent::__construct();
    }
}
class C extends A {}

$a = new A;
$a->__construct();
$b = new B;
$b->__construct();
$c = new C;
$c->__construct();

and the result is 121212

So, for now i will keep in mind: 
* dont mess with the constuctor of a class 
* do not use static variables in a constructor

Thanks for the time and work

The problem is that we're caching the constructor (and a few magic methods) in the class entry, but end up storing the parent constructor there -- which is always going to be the same unless it uses static variables, thus nobody noticed.

This is a bug, though I'm also increasingly tempted to write a proposal that changes the way we handle static variables in methods, and not use a separate static variable scope on inheritance.

I did end up writing that proposal (https://wiki.php.net/rfc/static_variable_inheritance). This means that as of PHP 8.1 the result will be as written in the "expected result".