PHP script – detect whether running under linux or Windows?

Check the value of the PHP_OS constant^Docs.

It will give you various values on Windows like WIN32, WINNT or Windows.

See as well: Possible Values For: PHP_OS and php_uname^Docs:

if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
    echo 'This is a server using Windows!';
} else {
    echo 'This is a server not using Windows!';
}