XMLHttpRequest is another way use javascript it is a dom object.
or you can use a Iframe to post your data.
<iframe id='myiframe' style=display:none ></iframe>
<script >
function callmeonkeyup()
{
myiframe.src = 'somepage.php?data='+whatistyped;
}
</script>
but consider whether or not it is supported by the broweser.