刷新时插入MySQL数据库的空白数据

Blank data added on refresh to mysql database how to get rid of??

Here is my code

https://docs.google.com/file/d/0B3bU0f9cR-ehM1E1Z1MzWHBNQkU/edit

Each web-developer have to follow 2 strict rules

1. All requests that change server stat (i.e. alter database) have to be performed using POST method
2. After processing POST method request, a GET method redirect have to be done

so, for example, add these lines after insert

header("Location:".$_SERVER['PHP_SELF']);
exit;