PHP Script - detect whether running under Linux or Windows?

PHP script - detect whether running under Linux or Windows or other Operating System? I don't have so much knowledge but can overcome with some solution. "PHP_OS" will solve this issue. Below is function to check if OS is Windows or not:

if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
    echo 'Windows!';
} else {
    echo 'Other Than Windows!';
}

PHP_OS will output below list of Operating System, not full list but I think it's almost all.

• CYGWIN_NT-5.1
• Darwin
• FreeBSD
• HP-UX
• IRIX64
• Linux
• NetBSD
• OpenBSD
• SunOS
• Unix
• WIN32
• WINNT
• Windows

You can see on Wikipedia for more information.