<?

$date=time();

$ip=getenv('REMOTE_ADDR');
$br=$_SERVER['HTTP_USER_AGENT'];

$len_online_inbase=mysql_num_rows(mysql_query('SEL ECT id FROM '.$table_online_user." WHERE ip='".$ip."' and br='".$br."' LIMIT 1"));

if($len_online_inbase==1){mysql_query('UPDATE '.$table_online_user.' SET date='.$date." WHERE ip='".$ip."' and br='".$br."' LIMIT 1");}
else{mysql_query('INSERT INTO '.$table_online_user." SET ip='".$ip."',br='".$br."',date=".$date);};

$date_time_out=$date-180; //// 180 - 3 минуты

$len_online_now=mysql_num_rows(mysql_query('SELECT * FROM '.$table_online_user.' WHERE date > '.$date_time_out));

echo 'сейчас: '.$len_online_now.' на сайте';

?>