Possible Values For: PHP_OS
PHP passes through the uname, except on Windows (WINNT) and Netware (Netware). See Wikipedia for a non-exhaustive list of values not mentioned in your question: CYGWIN_NT-5.1 IRIX64 SunOS HP-UX OpenBSD (not in Wikipedia)
superglobals
Warning “Do not Access Superglobal $_POST Array Directly” on Netbeans 7.4 for PHP
filter_input(INPUT_POST, ‘var_name’) instead of $_POST[‘var_name’] filter_input_array(INPUT_POST) instead of $_POST