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Date: Tue, 22 Sep 2015 12:53:07 -0700
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To: Sean DuBois <sean@siobud.com>
Cc: internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Data serialization of objects, want to iterate 'sealed'
 properties then dynamic ones
From: zardozrocks@gmail.com (j adams)

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Thank you, Sean. Still looking for a couple of answers...

> 1) 'Default Properties' or properties stored on the class (not object)
can be found on the zend_class_entry[0], they are just accessed by offset
[1]
> This isn't a stable/public API, but good for a cool hack!

I'm afraid I don't follow. Could you elaborate? I've seen one way to get
'default properties' from a zend_class_entry object:
zendClassEntry->default_properties;
This gets us a list of default properties. I've also seen
zendClassEntry->properties_info;
Which, if I'm not mistaken, involves more elaborate parsing logic but also
tells you whether properties are accessible.

Seems like numerous ways to skin a cat. What is the orthodox approach here?
Also, what do you suggest to distinguish 'sealed' (i.e., default)
properties from dynamic ones? Is there some counterpart to
default_properties that returns non_default_properties -- i.e., just the
dynamic ones? Or should I just get all of the object's properties and check
each key to see if it's one of the default_properties by searching a
HashTable of these default properties?


> 3) Never used this, but it seems to be to confirm that a mangled prop
name matches a zend_property_info *

Not sure I follow. We create a separate zobj of type zend_object using the
function:
    zobj = zend_objects_get_address(obj TSRMLS_CC);
And then use zobj to check access:
    if (zend_check_property_access(zobj, key, key_len-1 TSRMLS_CC) ==
SUCCESS) {

I find it odd that our native zval type would not encompass member
accessibility. I'm wondering if zend_object might be some kind of
historical add-on concept to expand very old PHP functionality or if
there's some reason for this distinct object type.



On Tue, Sep 22, 2015 at 12:32 PM, Sean DuBois <sean@siobud.com> wrote:

> On Tue, Sep 22, 2015 at 11:16:46AM -0700, j adams wrote:
> > I'm working on a data serialization routine wherein I must iterate
> through
> > an object's properties while distinguishing between "sealed" properties
> > (i.e., those specified by class definitions) and "dynamic" properties"
> > (i.e., those assigned ad-hoc to some object that are not party of any
> class
> > definition).
> >
> > I found the source of the php function get_object_vars():
> > http://lxr.php.net/xref/PHP_5_6/Zend/zend_builtin_functions.c#985
> > However, I am still pretty confused. PHP source is *full* of macros and
> has
> > basically no comments. Hoping for some tips to keep me on the right
> track.
> > I'm pretty sure I can get something kludgy working, but I want my code to
> > be orthodox and work well.
> >
> > QUESTIONS
> > 1) Sadly, this approach is unable to distinguish "sealed" properties from
> > dynamic ones. If anyone can refer me to some source (or outline a general
> > approach) which can first iterate sealed properties and then iterate only
> > dynamic ones, that would be extremely helpful.
> >
> > 2) What does zend_objects_get_address do? This reference looks very
> > different than the usual macro, e.g. Z_OBJ_HT_P
> >
> > 3) Am I correct in understanding that zend_check_property_access simply
> > checks if the property in question is availabe in the scope in which this
> > function call gets executed? Is this the canonical/orthodox way to make
> > this check?
> >
> > 4) What does zend_unmangle_property_name do? Why is this function changed
> > to zend_unmangle_property_name_ex in 5.5 and later?
> >
> > 5) Why do we call Z_ADDREF_PP(value) here? Is this reference counting to
> > prevent garbage collection?
> >
> > 6) An IS_INTERNED check is added in php 5.6 and yet the macro for
> > IS_INTERNED is zero. What's that all about?
> >
> > 7) The code looks quite different between the different versions:
> > 5.3 - http://lxr.php.net/xref/PHP_5_3/Zend/zend_builtin_functions.c#950
> > 5.5 - http://lxr.php.net/xref/PHP_5_5/Zend/zend_builtin_functions.c#982
> > 5.6 - http://lxr.php.net/xref/PHP_5_6/Zend/zend_builtin_functions.c#985
> > From what I can tell there is at least one difference between 5.3 and 5.6
> > -- zend_unmangle_property_name_ex does not exist before 5.5. Can anyone
> > recommend how to make code that'll work in 5.3-5.6? Also, with 7 coming
> out
> > I'd like it work there too.
> >
> > Any answers or assistance would be greatly appreciated.
> Hey,
>
> 1) 'Default Properties' or properties stored on the class (not object)
> can be found on the zend_class_entry[0], they are just accessed by offset
> [1]
>
> This isn't a stable/public API, but good for a cool hack!
>
> 3) Never used this, but it seems to be to confirm that a mangled prop name
> matches a
> zend_property_info *
>
> 4) [2] Is some good reading on property name mangling
>
> 5) [3] Pretty much! Refcount is just to keep track of when a zval can be
> destroyed
>
> Hopefully the more educated members of the list can follow up and fix my
> errors, but for now that
> will at least get you going/able to dive deeper.
>
>
> [0] http://lxr.php.net/xref/PHP_5_6/Zend/zend.h#488
> [1] http://lxr.php.net/xref/PHP_5_6/ext/reflection/php_reflection.c#3410
> [2]
> http://www.phpinternalsbook.com/classes_objects/internal_structures_and_implementation.html
> [3] http://www.phpinternalsbook.com/zvals/memory_management.html
>

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