opcache_compile_file() fails with Cannot redeclare function error when compiling multiple files with the same function

[joec4i]

Description

The following code:

compile-test.php

<?php
var_dump(opcache_compile_file(__DIR__ . '/releases/v1/functions.php'));

// expecting `bool(false)` since opcache_compile_file() shouldn't have executed the compiled file.
var_dump(in_array('foo', get_defined_functions()['user']));

// expecting successful compilation: `bool(true)`
var_dump(opcache_compile_file(__DIR__ . '/releases/v2/functions.php'));

releases/v1/functions.php

<?php
function foo(): string {
    return 'foo_v1';
}

releases/v2/functions.php

<?php
function foo(): string {
    return 'foo_v2';
}

Resulted in this output:

bool(true)
bool(true)
PHP Fatal error:  Cannot redeclare foo() (previously declared in /private/tmp/opcache/releases/v1/functions.php:4) in /private/tmp/opcache/releases/v2/functions.php on line 4

Fatal error: Cannot redeclare foo() (previously declared in /private/tmp/opcache/releases/v1/functions.php:4) in /private/tmp/opcache/releases/v2/functions.php on line 4
PHP Warning:  Zend OPcache could not compile file /private/tmp/opcache/releases/v2/functions.php in /private/tmp/opcache/compile-test.php on line 4

Warning: Zend OPcache could not compile file /private/tmp/opcache/releases/v2/functions.php in /private/tmp/opcache/compile-test.php on line 4
bool(false)

But I expected this output instead:

bool(true)
bool(false)
bool(true)

Additional Context: The issue happens on both cli and php-fpm. It seems to be similar to https://bugs.php.net/bug.php?id=66066 . While the use case in bug 66066 might be less common in the real world and probably should be avoided, it's a perfectly valid use case to run multiple releases with similar files under the same php-fpm instance.

Workaround Our current workaround is to compile different releases with different requests, i.e. PHP will happily process the following logics in two different requests.

compile-v1.php

<?php
var_dump(opcache_compile_file(__DIR__ . '/releases/v1/functions.php'));

compile-v2.php

<?php
var_dump(opcache_compile_file(__DIR__ . '/releases/v2/functions.php'));

opcache_get_status()['scripts'] shows that the two files have been compiled successfully.

    [/var/www/html/releases/v2/functions.php] => Array
        (
            [full_path] => /var/www/html/releases/v2/functions.php
            [hits] => 0
            [memory_consumption] => 992
            [last_used] => Fri Nov  1 11:32:01 2024
            [last_used_timestamp] => 1730460721
            [timestamp] => 1730458160
            [revalidate] => 1730460723
        )

    [/var/www/html/releases/v1/functions.php] => Array
        (
            [full_path] => /var/www/html/releases/v1/functions.php
            [hits] => 5
            [memory_consumption] => 992
            [last_used] => Fri Nov  1 11:31:58 2024
            [last_used_timestamp] => 1730460718
            [timestamp] => 1730458130
            [revalidate] => 1730460720
        )

PHP Version

PHP 8.3.13

Operating System

No response

[joec4i]

I have put my test setup in https://github.com/joec4i/opcache-compile-tests . Thanks!

[iluuu1994]

Hi @joec4i, thanks for your report, and sorry for the delay. I agree that at least the documentation is misleading.

https://www.php.net/manual/en/function.opcache-compile-file.php

This function compiles a PHP script and adds it to the opcode cache without executing it. This can be used to prime the cache after a Web server restart by pre-caching files that will be included in later requests.

The fix^1 is breaking though, so we may not fix it in any supported versions. It should also be discussed on the mailing list.

[danog]

I believe the removal of function caching is a bit of an overreaction: it was always known, to those who used it, that preloading will cache functions, and requires an include guard to avoid function redeclaration errors, and in fact it is a very useful feature.

There is nothing wrong with this behaviour, and it does what you expect it to do.

I believe I was slightly confused by a different issue I previously dealt with i.e. https://github.com/amphp/amp/issues/321