there are a few ways to do this, just one of these is via js:
<?
echo '<script language="JavaScript">
i=0;
timeri();
function timeri(){
if(i<10){
i=i+1;
}
tid=setTimeout("timeri()",100);
if(i==10){
clearTimeout(tid);window.location.href="'.$site.'";
}
}
</script>';
?>
edit the 100 in the timeout to configure the seconds;
1000 would be 10 seconds (cause i loops to 10);