以下内容将帮助您识别操作系统和浏览器，并将类添加到body标记中，以便在加载页面时参考。您可以修改整个过程，以便它确定要使用哪个下载链接。这就是我用来区分CSS的目的，但最终你想要的是识别操作系统。

strtolower( $_SERVER[\'HTTP_USER_AGENT\'] ); 标识正在使用的浏览器。getenv( \'HTTP_USER_AGENT\' ); 获取环境/操作系统。

<?php 
function os_browser_body_class( $class ) {
        $brwsr = array(
            \'msie\',
            \'firefox\',
            \'webkit\',
            \'opera\'
        );
        $os = array(
            \'Windows\',
            \'Mac\', //will include Mac OS & Apple iOS
            \'Macintosh\' //just Mac OS
        );
        $user_brwsr = strtolower( $_SERVER[\'HTTP_USER_AGENT\'] );
        $user_agent = getenv( \'HTTP_USER_AGENT\' ); 
        foreach( $brwsr as $name ) {
            if( strpos( $user_brwsr, $name ) > -1 ) {
                $class[] = $name;
                preg_match( \'/\' . $name . \'[\\/|\\s](\\d)/i\', $user_brwsr, $matches );
                if ( $matches[1] )
                $class[] = $name . \'-\' . $matches[1];
                return $class;
            }
        }
        foreach( $os as $name ) {
            if( strpos( $user_agent, $name ) > -1 ) {
                $class[] = $name;
                preg_match( \'/\' . $name . \'[\\/|\\s](\\d)/i\', $user_agent, $matches );
                if ( $matches[1] )
                $class[] = $name . \'-\' . $matches[1];
                return $class;
            }
        }
        return $class;
    }
    add_filter( \'body_class\', \'os_browser_body_class\' );
?>

<?php 
$user_agent = getenv( \'HTTP_USER_AGENT\' ); 
if( $user_agent == \'Windows\' ) :
    $app_download = \'http://downloadurl.com/to-your-app/windows-version.zip\';
elseif( $user_agent == \'Mac\' ) :
    $app_download = \'http://downloadurl.com/to-your-app/mac-version.zip\';
endif;  
?>

echo $app_download;