FILE_EXTERNAL breaks __DIR__

[Bilge]

Q	A
PHPUnit version	11.3.6
PHP version	8.2.15
Installation Method	Composer

Summary

An external PHP source file referenced by FILE_EXTERNAL breaks assumptions about __DIR__ pointing to directory of the source file so referenced.

Current behavior

It seems __DIR__ resolves to the directory of the test file including the source so specified in the FILE_EXTERNAL section, instead of the external file itself.

How to reproduce

# my.phpt

--FILE_EXTERNAL--
../external.php

# ../external.php

echo __DIR__, "\n";

Expected behavior

Should print the parent directory of my.phpt.
Currently prints the same directory as my.phpt.