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Date: Tue, 20 Jan 2015 10:58:29 -0700
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Subject: Static Closures and PHP 7
From: levim@php.net (Levi Morrison)

Internals,

Last year I "fixed" the behavior of closures in a few regards, which
were included in PHP 5.5.14 and 5.6 (unsure on exact version):

  - Static closures properly use late-static binding on `static::`
calls from inside static methods.
  - Non-static closures in static methods are automatically promoted
to static closures

The first item is undoubtably a bug-fix (see http://3v4l.org/lVenA for
an example).

The second item, however, is a bit more questionable. Take as an
example this code: http://3v4l.org/YMYeu (located at bottom of email
as well). When in global scope using an anonymous function with a
$this->ptr does not error, but when we are in a static method there is
a warning at bind-time and a fatal when the method is called.

Before my changes I could have said this was a bug with confidence.
After my change, however, it means that the closure is implicitly
static and therefore cannot use a $this pointer. My patch didn't break
anything, but allowed people to use late static binding in non-static
closures inside of static methods (I recommend reading that sentence
again).

Logically, I am surprised by this behavior. I would think that
anything permissible for a closure in global scope is also permissible
for a closure in static scope.

What do you guys and gals think?


<?php

class A {
    function hi() {
        return "hello";
    }
}

// in global scope
$f = function() {
    return $this->hi(); // no warnings
};
$a = new A();
$g = $f->bindTo($a); // no warnings
echo $g(), PHP_EOL; // no warnings

class B extends A {
    // in a static function
    static function make() {
        return function() {
            return $this->hi(); // fatal error when called
        };
    }
}

$h = B::make();
$i = $h->bindTo($a); // warning
echo $i(), PHP_EOL; // fatal error