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Date: Thu, 15 Mar 2012 17:39:00 +0000
Message-ID: <CAKxcST-a2xjXJSEk767Wd34nAcj5Xu+EaQ+-TvboDc4K5izGsw@mail.gmail.com>
To: Nikita Popov <nikita.ppv@googlemail.com>
Cc: Patrick ALLAERT <patrickallaert@php.net>, Klaus Silveira <klaussilveira@php.net>, 
	PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Small question about performance
From: dragoonis@gmail.com (Paul Dragoonis)

On Thu, Mar 15, 2012 at 4:54 PM, Nikita Popov <nikita.ppv@googlemail.com> w=
rote:
> On Thu, Mar 15, 2012 at 5:22 PM, Patrick ALLAERT <patrickallaert@php.net>=
 wrote:
>> 2012/3/15 Nikita Popov <nikita.ppv@googlemail.com>:
>>> If I am understanding the text correctly it is saying that
>>> =A0 =A0$f1 =3D f1();
>>> =A0 =A0$f2 =3D f2($f1);
>>> =A0 =A0$f3 =3D f3($f2);
>>> is using more memory than
>>> =A0 =A0$f3 =3D f3(f2(f1()));
>>>
>>> For me this doesn't make any sense. In the latter case PHP will also
>>> create temporary variables to store the return values. There should be
>>> no difference in memory consumption.
>>
>> It does make sense to me.
>>
>> In the first case, when calling f3(), $f1 is still referenced.
>> In the second case, when calling f3(), the result of f2() is
>> referenced, but there is no more active reference to the result of
>> f1().
> I don't really know when PHP frees temporary variables, but my guess
> was that they are freed when the scope is left.

Each variable has a refcount, then that hits 0 it can be freed up.

>
> If that is not true, then forget whatever I said.
>
> But if it is true, then there is no inherent difference between the
> two version. The only difference is that explicit $variables would
> need an entry in the active symbol table, which is pretty much
> negligible.
>
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