Note that this function is not defined on Windows PHP.
(PHP 4, PHP 5, PHP 7)
posix_getuid — Return the real user ID of the current process
Return the numeric real user ID of the current process.
Returns the user id, as an integer
Example #1 Example use of posix_getuid()
<?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