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Date: Sat, 2 Aug 2025 18:19:03 +0100
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Subject: Re: [PHP-DEV] Protected inheritance hierarchies
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")

On 02/08/2025 15:09, Rob Landers wrote:
> I’m not sure what you mean? https://3v4l.org/WKILh#v8.4.10
>
> There is clearly shadowing going on.


There's a lot of confusing code in that example, so I'm not really sure 
what it's illustrating.

This example seems more to the point: https://3v4l.org/FVhXa

Regardless of whether you look up the reflection property on the parent 
or the child, it points to the same slot for property 'v'

In contrast, the same reflection code for a private property finds both 
values stored in the object: https://3v4l.org/S7GmM

You can see the same result with var_dump (and serialize, and 
debug_zval_dump, ...): https://3v4l.org/FqecC


I think the relevant code is this, in zend_declare_typed_property: 
https://heap.space/xref/php-src/Zend/zend_API.c?r=78d96e94fa8e05dd59d03aa4891fa843ebc93ef8#4661

if (access_type & ZEND_ACC_PUBLIC) {
     property_info->name = zend_string_copy(name);
} else if (access_type & ZEND_ACC_PRIVATE) {
     property_info->name = zend_mangle_property_name(ZSTR_VAL(ce->name), 
ZSTR_LEN(ce->name), ZSTR_VAL(name), ZSTR_LEN(name), 
is_persistent_class(ce));
} else {
     ZEND_ASSERT(access_type & ZEND_ACC_PROTECTED);
     property_info->name = zend_mangle_property_name("*", 1, 
ZSTR_VAL(name), ZSTR_LEN(name), is_persistent_class(ce));
}

For a private name, the mangled name includes the class where it's 
defined, which is where the shadowing comes from: the final merged 
symbol table has two differently named slots.

But for a protected name, the prefix is just "*", so it's the same slot 
no matter how many times it appears in the hierarchy, just like for 
public properties (whose names aren't mangled at all).


How this relates back to the original example in the thread, I'm not 
sure, but it's definitely not "shadowing" in the same sense as a private 
property.

-- 
Rowan Tommins
[IMSoP]