Note that this function is not defined on Windows PHP.(PHP 4, PHP 5, PHP 7, PHP 8)
posix_getuid — 現在のプロセスの実際のユーザー ID を返す
この関数にはパラメータはありません。
ID を表す整数値を返します。
例1 posix_getuid() の使用例
<?php
echo posix_getuid(); //10000
?>On more modern systems the posix functions have split out into the php-process package
Installed Packages
Name         : php-process
Version      : 7.2.24
Release      : 1.module_el8.2.0+313+b04d0a66
Architecture : x86_64
Size         : 100 k
Source       : php-7.2.24-1.module_el8.2.0+313+b04d0a66.src.rpm
Repository   : @System
From repo    : appstream
Summary      : Modules for PHP script using system process interfaces
URL          : http://www.php.net/
License      : PHP
Description  : The php-process package contains dynamic shared objects which add
             : support to PHP using system interfaces for inter-process
             : communication.None of the posix_* functions are available under Windows, since Windows is not POSIX compliant. But there seems to be / was an optional software package available, see here: https://en.wikipedia.org/wiki/Microsoft_POSIX_subsystem