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Date: Sat, 7 Jul 2018 18:03:42 +0100
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Subject: Re: [PHP-DEV] [RFC] Typed Properties
From: rowan.collins@gmail.com (Rowan Collins)

On 06/07/2018 21:57, Nicolas Grekas wrote:
>
>> if ((new ReflectionReference($array[$key]))->getRefcount() > 2) {
> I just realized that this interface would suffer from a significant
> drawback: it would trigger COW when iterating over immutable arrays,
> defeating the shared-memory optimization provided by OPcache.

Any implementation of this that acts like a normal function / 
constructor call is going to suffer from the same problems as 
debug_zval_dump: passing a variable from one scope to another will 
change the properties of that variable. If you accept the variable by 
reference, you'll duplicate the data if it's part of a COW set (which 
has nothing to do with OpCache by the way, it's been a core part of the 
engine since at least 5.0); if you accept it by value, you'll duplicate 
the data if it's part of a reference set. Either way, you're going to 
change the refcount on the zval, hence the awkward 2 in Bob's example.

Previous discussions of that function concluded that the only "correct" 
way to implement this would be as a language feature rather than a true 
function - if the compiler issues a specific OpCode, it can pull the 
zval straight out of the symbol table, without interfering with it.

Maybe the two concepts could be combined, and the language feature 
generate a Reflection object? e.g.

$reflection = reflect_variable($var);
if ( $reflection->isReference() ) {
     $types = $reflection->getReferencedTypes();
}



> An interface like new ReflectionReference($array, $key) would be free from
> the issue. Combined with get_defined_vars() and the (array) operator for
> objects, we can inspect any PHP data structure or scope also this way.

Yuck. Even if this solves the issue of supporting both ref and non-ref 
variables, you still end up having to compensate for the wrong refcount, 
and the resultant code would be ugly as sin.

Regards,

-- 
Rowan Collins
[IMSoP]