Yes, very possible.. Just need to use sockets. >:D You'd write a script in php that recieves get variables, then have mirc visit the web page, and set the values. Eg..
If you have the page submit.php and you would like to send it values of $_GET["fname"] and $_GET["lname"], you could have mirc visit
www.mysite.com and send a get request to $+(/submit.php?fname=,%fname,&,lname=,%lname) >:D
