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Date: Tue, 17 May 2016 16:28:14 +0200
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To: Jesse Schalken <me@jesseschalken.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Do symbol references always go through a hash table?
From: nikita.ppv@gmail.com (Nikita Popov)

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On Tue, May 17, 2016 at 3:03 PM, Jesse Schalken <me@jesseschalken.com>
wrote:

> Hi Internals,
>
> I'd like to know whether references to
> classes/functions/methods/properties/variables always go through a hash
> table at runtime, or if the name is optimised into a pointer or fixed
> offset. I recall seeing such an optimisation for local variables, but what
> about the others?
>
> Thanks
>

A property access $foo->bar (where "bar" is a literal and not the result of
an expression) uses a polymorphic runtime cache, which will store the class
entry and property offset the first time the instruction is executed.
Afterwards, if $foo is an instance of the same class, we will directly use
this offset. Otherwise, a full lookup from the property name table with
visibility checks and all those other bells an whistles has to be performed.

The same holds for pretty much all other symbol references as well, so
classes, functions, methods, etc.

Nikita

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