php 判断平台是安卓还是ios

public function testagent(){
       if(strpos($_SERVER['HTTP_USER_AGENT'], 'iPhone')||strpos($_SERVER['HTTP_USER_AGENT'], 'iPad')){
           echo 'systerm is IOS';
       }else if(strpos($_SERVER['HTTP_USER_AGENT'], 'Android')){
           echo 'systerm is Android';
       }else{
           echo 'systerm is other';
       }
   }