PHP判断用户访问的操作系统,以及iOS的设备

<?php
function getOS()
{
$agent = strtolower($_SERVER['HTTP_USER_AGENT']);
if(strpos($agent, 'windows nt')) {
$platform = 'windows';
} elseif(strpos($agent, 'macintosh')) {
$platform = 'mac';
} elseif(strpos($agent, 'ipod')) {
$platform = 'ipod';
} elseif(strpos($agent, 'ipad')) {
$platform = 'ipad';
} elseif(strpos($agent, 'iphone')) {
$platform = 'iphone';
} elseif (strpos($agent, 'android')) {
$platform = 'android';
} elseif(strpos($agent, 'unix')) {
$platform = 'unix';
} elseif(strpos($agent, 'linux')) {
$platform = 'linux';
} else {
$platform = 'other';
}
return $platform;
}

echo getOS();