Issue5592Test fails when registering an error handler in an auto_prepend_file

[kkmuffme]

Q	A
PHPUnit version	11.1.3
PHP version	8.2.x
Installation Method	both

Summary

When using php.ini auto_prepend_file where the file contains an error handler (I assume same issue with exception handlers) like

set_error_handler(static fn () => false);

test Issue5592Test fails:

-There was 1 risky test:
+There were 2 risky tests:

Current behavior

phpunit test suite fails

How to reproduce

./phpunit after adding error handler like in summary

Expected behavior

No error

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This matters beyond this specific test, as the number of "risky" tests differs depending on whether or not an error/exception handler is defined in an auto_prepend_file or not.
Possibly this also happens when a PHP (PECL) extension defines an error/exception handler.