How can estimate package sent and received in a computer?

I using PHP language, I want to estimate Internet speed. So I must know number of packets sent and received in a computer. Is there anyone know about that? Could you help me?
Thanks alot
Carol

1 take timestamp

2 send known ammount of bytes to the client

3 take timestamp

4 calculate

Very well put _Leo_, I was going to say almost the exact same thing, except I would have said subtract first from the second then divide the filesize by the time and viola you have your answer in KB/Sec or however large your file is. But yours does the exact same thing mine would do. There are probably scripts already made for what you are trying to do. You should probably either google it, or search on http://www.hotscripts.com

Thank you very much. I will do in that way.
And could you tell me the relation between number of packets in, packets out and speed in MBps?
Thanks again.