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Date: Mon, 26 Nov 2012 21:03:35 -0800
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To: Rasmus Lerdorf <rasmus@lerdorf.com>
Cc: Raymond Irving <xwisdom@gmail.com>, PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] HHVM and PHP
From: pollita@php.net (Sara Golemon)

>> I've being reading about HHVM and the numbers are looking great but I was
>> just wondering if we will we ever see something like HHVM being added to
>> the PHP core?
>
> No, not likely. Maybe an LLVM-based JIT one day, but the HHVM approach
> is not something any of us are looking at.
>
To echo Rasmus' reply: No.

HHVM is a reimplementation of the PHP language from the ground up, so
logically speaking "adding it to the PHP core" doesn't actually make
sense.  They're different birds from the get-go.

PHP could adopt a similar strategy of translating bytecode to native
machine code (again echoing Rasmus' reply), but that would be a large
undertaking by itself, and adapting zval unions to static type
analysis is a whole other layer of complexity beyond that.

The important thing to keep in mind is what each implementation is
good at, and what it's not.  As the maintainer of the OSS version of
HipHop (HHVM), I'll be the first to admit that the official PHP engine
and runtime have a broader range of platform/architecture support, and
stronger community, and a larger library of extensions and
functionality behind it.  Also, because of it's lifecycle design, PHP
outperforms HHVM on single-run command-line scripts.

On the other hand, HHVM does outperform Apache+PHP for web requests
quite well.  Facebook would need at least 5x as many web-servers (and
we use a lot as it is) if we were using normal PHP.  That's not to say
PHP isn't fast, but interpreted bytecode using loose typing will never
keep pace with native machine code and strict typing.

Standard Disclaimer: Yes, front-end CPU time isn't the end-all be-all
of optimization.  You should always start with your data access layer
and the efficiency of the scripts you write.

-Sara

P.S. - I do disagree with Rasmus' statement about none of us looking
at fitting a JIT into PHP. ;)