Am not able to send data to phpmyadmin database using sim900a via TCP/IP.

ok thanks, so what shoul i do?

When in doubt,
run in circles,
scream and shout.

When that doesn't work, put the Arduino in a box and nail it shut.

Learn how to make one PC make a GET request to a server on another PC. When you can do that, you can get the Arduino back out, and make it make the GET request PROPERLY.

I've told you TWICE EXACTLY what the problem is, but you are not listening.