php - Determine if operating system is Mac -

i have been doing lot of googling try , find simple, easy php script identify if user on mac or not.

i want use tell users if keyboard shortcut telling them "control" or "command". don't need know browser or anything, if computer mac.

here outline of i'm asking possible:

if (operating_system == mac) {     echo "command"; } else {     echo "control"; } 

create page: identifier.php

<?php $user_agent = getenv("http_user_agent");  if(strpos($user_agent, "win") !== false) $os = "windows"; elseif(strpos($user_agent, "mac") !== false) $os = "mac"; ?> 

then include on header of site.

after can use this:

<?php if($os === "windows") {  } elseif($os === "mac") {  }  ?> 

edit:

for windows phone:

if (strpos(strtolower($_server['http_user_agent']), 'windows phone os') > 0) {     $mobile_browser = 1;   }