So is there any tutorial or any thing that demonstrate this issue ???
No but it is not difficult, you just never did it, these are the steps to be taken
1) Add an ethernetshield to the ATMEGA
2) install APache and PHP on the system with MySQL server
3) make a HTTP POST message from the Arduino to the PHP Apache,
4) PHP will store it into MySQL
Should also be possible over a serial line, but I have no experience with PHP and Serial . [The integration between PHP and MySQL is very good]
Al these code-parts can be found on this forum, as I have seen them pass by, so you only need to search and combine...