php如何判断页面是在PC端还是移动端

php如何判断页面是在PC端还是移动端，下面是直接上代码：

public function isMobile(){
  $useragent = isset($_SERVER['HTTP_USER_AGENT']) ? $_SERVER['HTTP_USER_AGENT'] : '';
  $useragent_commentsblock = preg_match('|\(.*?\)|',$useragent,$matches)>0?$matches[0]:'';
  function CheckSubstrs($substrs,$text){
    foreach($substrs as $substr)
      if(false!==strpos($text,$substr)){
        return true;
      }
    return false;
  }
  $mobile_os_list = array('Google Wireless Transcoder','Windows CE','WindowsCE','Symbian','Android','armv6l','armv5','Mobile','CentOS','mowser','AvantGo','Opera Mobi','J2ME/MIDP','Smartphone','Go.Web','Palm','iPAQ');
  $mobile_token_list = array('Profile/MIDP','Configuration/CLDC-','160×160','176×220','240×240','240×320','320×240','UP.Browser','UP.Link','SymbianOS','PalmOS','PocketPC','SonyEricsson','Nokia','BlackBerry','Vodafone','BenQ','Novarra-Vision','Iris','NetFront','HTC_','Xda_','SAMSUNG-SGH','Wapaka','DoCoMo','iPhone','iPod');
  
  $found_mobile = CheckSubstrs($mobile_os_list,$useragent_commentsblock) || CheckSubstrs($mobile_token_list,$useragent);
  
  if ($found_mobile){
      return true;
  }else{
      return false;
  }
}

if (isMobile()){
  echo '我是手机端';
}else{
  echo '我是PC端';
}
?>