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Date: Wed, 23 Oct 2013 20:10:17 +0200
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To: Dmitry Stogov <dmitry@zend.com>
Cc: Julien Pauli <jpauli@php.ne>, David Soria Parra <dsp@php.ne>, Stas Malyshev <smalyshev@sugarcrm.com>, 
	PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Improved performance of array_maerge() and func_get_args()
From: patrickallaert@php.net (Patrick ALLAERT)

2013/10/23 Dmitry Stogov <dmitry@zend.com>:
> Hi,
>
> I'm proposing two simple patches that eliminate a lot of useless zval
> copying.
> For example they remove only about 800 calls to zend_hash_copy() (25%) on
> each request to wordpress-3.6.0 home page and make it 2-4% faster.
>
> It's not a questions about master branch, but I think it is also safe to
> commit them into PHP-5.4 and PHP-5.5.
>
> Any objections?
>
> https://gist.github.com/dstogov/7117623
>
> https://gist.github.com/dstogov/7117649
>
> Thanks. Dmitry.

That sounds really good.

Note that in many performance investigations I made, array_merge() was
often one of the cause of some unnecessary overhead, however, most of
the times this function was used was in fact to merge arrays that were
in fact *hashes* (dictionary, map,...) and not really *arrays*. In
those cases, the performance fix is simply to use "$y + $x" instead of
"array_merge($x, $y).

Are all those array_merge() of wordpress really made to merge *arrays*
rather than *hashes*?

Is the gain constant for all cases of array_merge(), with numeric
indices vs string ones?

Patrick