PHP关于REQUEST一点有关问题

PHP关于REQUEST一点问题
   $doing=$_REQUEST['doing'];

   switch($doing)
  {
      case "yingwen":
             
                  if(isset($_REQUEST['english']))
                {        echo"别出来了";
 }  else
                       { echo "请输入英文";} 
                            break;      
          
      case "zhongwen":
                          
if(isset($_REQUEST['chinese']))
                {        echo"别出来了";
 }  else
                       { echo "请输入中文";} 
                            break;
   
                        
  }         
?>
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