I'm sorry I'm opening this bug again, but I was told that my bug was something like 
http://bugs.php.net/bug.php?id=10599&edit=1
but I don't think it's true because the problem there was in HTML; I don't have any HTML code here.

I have the following script: 

function log_query($q) {
    echo $q."<br/>\n";
    return mysql_db_query('logs', $q);
}

global $REMOTE_ADDR, $HTTP_USER_AGENT, $HTTP_SESSION_VARS;
$agent = addslashes($HTTP_USER_AGENT);
$logged_user = $HTTP_SESSION_VARS['userinfo']['username'];

$query = "update ichb_hits set count = count + 1 where ip =
'$REMOTE_ADDR' and user = '$logged_user' and agent = '$agent' and
 date > (now() - INTERVAL 1 HOUR)";
$res = log_query($query);
if (@mysql_affected_rows() <= 0) {
    $query = "insert into ichb_hits (ip, count, date, user, agent)
values ('$REMOTE_ADDR', 1, now(), '$logged_user', '$agent
')";
    log_query($query);
}

This script is in a file called 'log.php'; I include this log.php only
once. The update query is displayed only once, but the count increases
two times; not by 2, but two times at an interval of a quarter of a
second.
If I access the file log.php by itself it executes the query corectly!

Configure Command : './configure' '--with-mysql' '--with-gd'
'--with-zlib' '--with-apxs' 
Try http://db.lumina.ro/info.php for details about PHP installation.