This also happens on current master.  It works fine if file2.php
is inlined.  Neither a debug build nor valgrind
(ZEND_DONT_UNLOAD_MODULES=1 USE_ZEND_ALLOC=0) report a memory
leak, though.

Thanks for confirming.  If it helps, the same problem also happens if you put "return;" as the first line of file2.php like the below, so it seems related to compiling perhaps, rather than executing.

file2.php:
<?php
return;

$test_function = function()
{
};

I'm seeing the same problem even when I don't use a closure and instead just assign a variable.  I also saw the same problem, but to a lesser extent, with a print command.  I filed a report for that in Bug #78076, but it seems like there may be a common problem related to repeated requires/includes?

I manage to reproduce consistently the issue on all PHP 7.x versions

https://github.com/goetas/symfony-mem-leak contains the repo to reproduce the issue

https://travis-ci.org/goetas/symfony-mem-leak/builds/551488795 is one build that shows the issue on Travis

Discovered while trying to solve https://github.com/symfony/symfony/issues/32220

This bug is pretty serious when integrating the symfony dependency injection container in reactphp, phppm or swoole applications.

This https://travis-ci.org/goetas/symfony-mem-leak/builds/551710669 shows the leak in the default configuration of the symfony dependency injection

This leak is partially fixed in PHP 8.1. There's still a memory leak, but it's a constant leak of ~250 bytes per overwritten closure now.

Problem occurs not only with closures but also with anonymous classes.

if (!class_exists(Test::class)) {
    class Test {
    }
}

is leaking too, even if the the if condition is satisfied only once, test https://github.com/php/php-src/pull/7562/files . Seems to be fixed in PHP 8.1, but only when opcache is enabled (which is not by default for CLI).