简单的会话示例不起作用

我写了这个小会话脚本,我看到它不起作用.

  
  
  
  

Hello $username";
  }

  else {
  echo "
OUT!
"; 
  echo "
";
  echo "";
  echo "
";
  }

  ?>

我无法弄清楚哪个部分是错的.看起来对m来说都很好但是肯定有些不对劲.

像这样的东西？

    

      
      
      
      

    Hello $username";
      }

else if($username) {
      echo "
Hello $username
";
      }

      else {
      echo "
OUT!
"; 
      echo "
";
      echo "";
      echo "
";
      }

      ?>