Newcomer, PHP pre-processing, Magic Constants __FILE__ and __LINE__ override with #line like in C

Hi,

I'm a newcomer here. I came from https://wiki.php.net/rfc/howto.

TL;DR: I want to know if a proposal of a #line parsing to alter FILE and LINE in PHP like it exists in C could be a good idea.

I've searched about LINE and FILE in mailing archives and wiki, I don't really find things matching. I hope it's not because "__" are stripped before search. "Magic constants" didn't help neither. Let me know if I am rethinking and old thing already imagined here in the past.

Background / use case: I think at first about webservices, maybe the useful also with browser/human-facing use cases.

With PHP, it's hard to get high responsiveness under load if user code start by loading a composer's autoload.php, then (lazy) loads a whole framework with 10+ dependencies, then execute 1 SQL request, 1 json_encode() then output and exit. Even with "Slim" framework that should be minimal, using only the route feature, I see "strace" counting 200+ file-related syscalls per request with recent linux/debian/apache/php-fpm.

It's not so hard to get it better with other langages : when they are compiled, or when framework loading happens at server start and to at each request.

Web projects have more and more a "compilation" phase for minimising JS, for proprocessing scss to css, it is possible to hook it some PHP processing too.

In my university, I started using a purpose-written PHP Preprocessor to minimize runtime dependency loading. It only understands #include like in C. From a src/mywebservice/v1/some-endpoint.php it will generate and build/mywebservice/v1/some-endpoint.php with all #include "some/path/somedep.php" replaced by the file's contents.

So the generated some-endpoint.php have no run-time dependency at all: no autoload, no include(), no require(). I think it evens maximize the gains with APC caching.

The preprocessor also generate things like #line 2 "some/path/somedep.php" where an #include was encountered, then a thing like #line 47 "src/mywebservice/v1/some-endpoint.php" right after the end of the inclusion. In C, a great concrete example of #line importance is working with a flex/bison parser generator.

If PHP parser interpret #line as in C, FILE and LINE Magic Constants will be changed to source file and line, instead of generated file and line. It could greatly improve development write-then-rerun cycle. (missing ";" at line NN , other PHP Errors, Exception details/traces)

I hope it could unlock many use cases where "big" PHP frameworks get really hard time to try to compete with other languages equivalents.

Do you think it's an idea that is suitable to discuss, improve and submit as an RFC ?

Regards,

--

Ludovic Pouzenc
www.pouzenc.fr

--

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Hi Ludovic,

I can’t comment much on the actual change in the parser you’re asking about, but it sounds to me like preloading (https://www.php.net/manual/en/opcache.preloading.php https://www.php.net/manual/en/opcache.preloading.php, introduced via https://wiki.php.net/rfc/preload https://wiki.php.net/rfc/preload) might be a workable solution that’s already available?

Cheers

Stephen

Hi,

I'm a newcomer here. I came from https://wiki.php.net/rfc/howto.

TL;DR: I want to know if a proposal of a #line parsing to alter
FILE and LINE in PHP like it exists in C could be a good idea.

I've searched about LINE and FILE in mailing archives and wiki,
I don't really find things matching. I hope it's not because "__" are
stripped before search. "Magic constants" didn't help neither. Let me
know if I am rethinking and old thing already imagined here in the past.

Background / use case: I think at first about webservices, maybe the
useful also with browser/human-facing use cases.

With PHP, it's hard to get high responsiveness under load if user code
start by loading a composer's autoload.php, then (lazy) loads a whole
framework with 10+ dependencies, then execute 1 SQL request, 1
json_encode() then output and exit. Even with "Slim" framework that
should be minimal, using only the route feature, I see "strace" counting
200+ file-related syscalls per request with recent
linux/debian/apache/php-fpm.

It's not so hard to get it better with other langages : when they are
compiled, or when framework loading happens at server start and to at
each request.

Web projects have more and more a "compilation" phase for minimising JS,
for proprocessing scss to css, it is possible to hook it some PHP
processing too.

In my university, I started using a purpose-written PHP Preprocessor to
minimize runtime dependency loading. It only understands #include like
in C. From a src/mywebservice/v1/some-endpoint.php it will generate and
build/mywebservice/v1/some-endpoint.php with all #include
"some/path/somedep.php" replaced by the file's contents.

So the generated some-endpoint.php have no run-time dependency at all:
no autoload, no include(), no require(). I think it evens maximize the
gains with APC caching.

The preprocessor also generate things like #line 2
"some/path/somedep.php" where an #include was encountered, then a thing
like #line 47 "src/mywebservice/v1/some-endpoint.php" right after the
end of the inclusion. In C, a great concrete example of #line importance
is working with a flex/bison parser generator.

If PHP parser interpret #line as in C, FILE and LINE Magic
Constants will be changed to source file and line, instead of generated
file and line. It could greatly improve development write-then-rerun
cycle. (missing ";" at line NN , other PHP Errors, Exception details/traces)

I hope it could unlock many use cases where "big" PHP frameworks get
really hard time to try to compete with other languages equivalents.

Do you think it's an idea that is suitable to discuss, improve and
submit as an RFC ?

Regards,

It sounds like there are numerous existing approaches to address the situation you describe that are already in use and far more effective than making constants stealthily dynamic.

1. Opcache preloading, introduced in PHP 7.4.
2. Disable the stat calls on opcache, so it doesn't even check the disk at all once something is in cache.
3. Use a persistent-process tool like React PHP, AmPHP, Revolt, and the like, so it functions more like Node.js instead of using PHP-FPM.

I think you're also greatly over-estimating how large the startup cost is in practice. It's real, certainly, but unless you have several nested microservices a well-made framework should have a fairly small overhead.

--Larry Garfield