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To: Rowan Tommins <rowan.collins@gmail.com>, "internals@lists.php.net"
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Thread-Topic: [PHP-DEV] Autoloading functions/consts without a performance
 impact
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Date: Fri, 3 Jan 2020 14:39:09 +0000
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Subject: Re: [PHP-DEV] Autoloading functions/consts without a performance
 impact
From: tysonandre775@hotmail.com (tyson andre)

> If we cache the resolution to global function at line 2, removing that li=
ne=0A=
> changes the rest of the program. If we don't cache it there, then what=0A=
> happens if we run this code in a loop?=0A=
=0A=
It (and my proposed autoloader change)=0A=
changes it for that call (at that opcode, i.e. for the call at that line an=
d column).=0A=
PHP's caching does not cache it for other calls within the same file.=0A=
If that call opcode was within a function or loop, however,=0A=
subsequent calls would use the cached resolution.=0A=
=0A=
> namespace Foo;=0A=
> echo strlen('hello'); // Finds a global function at step 2, so doesn't=0A=
> trigger the autoloader=0A=
> echo \Foo\strlen('hello'); // Explicitly namespaced function, so triggers=
=0A=
> the autoloader=0A=
> echo strlen('hello'); // Should this run \strlen or Foo\strlen?=0A=
=0A=
The example you were thinking of would call \strlen on line 2, \Foo\strlen =
on line 3, and \Foo\strlen on line 4.=0A=
(because the caching is per-opcode, not per-file or per-namespace)=0A=
=0A=
> We've never prioritized fixing this issue,=0A=
> but implementing the proposed autoloading behavior would make fixing it e=
ssentially impossible, as we certainly can't perform an autoloader invocati=
on on each call.=0A=
=0A=
If we skip autoloading ambiguous calls in the current namespace,=0A=
then we wouldn't have to perform an autoloader invocation every call,=0A=
and the problem of fixing that bug would be unchanged.=0A=
I marked step 3 as optional because there were arguments for/against it.=0A=
=0A=
-Tyson=