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Date: Sat, 24 Nov 2018 13:19:15 +0000
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Subject: Re: [PHP-DEV] [mini-RFC] Disable opcache per script using
 "declare(cache=0)"
From: rowan.collins@gmail.com (Rowan Collins)

On 23/11/2018 23:49, Zeev Suraski wrote:
> I'm not sure if you're missing anything fundamental - it's just that 
> the preload.php file Dmitry's referring to (the one that's responsible 
> to loading all the other files) - is one file that's pretty much by 
> definition, will be of no use at any later point in the lifetime of 
> the server.  It preloads other files (which of course, should very 
> much persist in the opcache memory) - but once it's done, it's done.  
> That's why it kind of makes sense not to cache it.


Ah, OK, so it's more a case of "don't bother caching" rather than "must 
avoid caching" then?

I think making it automatically uncached might be a bit confusing, and a 
source of future "gotchas". While it's *logical* for the INI setting to 
reference a stub file with nothing but includes, the feature as 
described in the RFC doesn't actually *require* this; it would be 
perfectly possible for someone to put a bunch of definitions in 
"preloaded_functions.php" and reference that one file directly in the 
preload directive. On the flip side, it's likely that frameworks will 
start shipping with their own preload helpers, so that you'd have 
"preload_all.php" reference "symfony/preload.php", and want to exclude 
*both* from the cache.

Thinking about it, I'm not clear exactly what a "do not cache" directive 
would mean in a preloaded file, since preloading is more than just 
caching. For instance, if "class A" is declared in a preloaded file with 
declare(cache=0), then "class B extends A" is declared in a preloaded 
file with caching enabled, how will class B be treated? Will the file 
containing class B be cached, but need to be referenced in an "include" 
statement in each request? Again, people will *probably* be using file 
structures and autoloaders that make this trivial, but the language 
doesn't require that.

Regards,

-- 
Rowan Collins
[IMSoP]