posix_geteuid

if you for some reason need the euid without depending on php-posix being available, try<?phpfunction geteuid_without_posix_dependency(): int{    try {        // this is faster if available        return \posix_geteuid();    } catch (\Throwable $ex) {        // php-posix not available.. fallback to hack        $t = tmpfile();        $ret = fstat($t)["uid"];        fclose($t);        return $ret;    }}

Please note the example code shown above is invalid and will fail, since UID 10001 cannot use posix_seteuid to change its UID to 10000