$sql=mysql_query("SELECT FROM users (username, password, email) WHERE username=$fusername");
 if(mysql_num_rows($sql)>=1)
   {
    echo"name already exists";
   }
 else
    {
   //insert query goes here
    }

您可以从数据库中检查用户是否存在，然后粘贴代码

you can check from database whether user exists and then paste the code