allow ini_set('error_log',...) with in-memory stream

Description

calling ini_set('error_log', $logger) seems to expect $logger to be a filesystem path (or a magic identifer like "syslog").

is it possible to pass in a memory stream?

use-case: in phpunit we want to capture all output a possible code beeing tested might write into error_log.
I have implemented this feature with a tmpfile() in https://github.com/sebastianbergmann/phpunit/pull/6118 but IMO it would be cleaner and more efficient (no filesystem IO) if I could pass in a memory stream like php://memory or php://temp:

        $stream = fopen('php://temp', 'rw');
        $errorLogPrevious = ini_set('error_log', $stream);

Iniziate tracciando il modo in cui ini_set('error_log', ...) gestisce i percorsi del filesystem e gli identificatori magici come "syslog". Esaminate la pull request collegata di PHPUnit relativa all’attuale workaround con tmpfile() e definite il comportamento supportato per php://memory o php://temp, compreso come verrebbe verificato il completamento.