Format your SQL statement like this:
Code:
$sql = "INSERT INTO userlogging
( ID, date, time, IP, browser, referer )
VALUES ( '', '$date', '$time', '$ip', '$useragent', '$referer' )";
You mentioned about variable names being in brackets. In this case I will assume that your variables are coming from an array called "clean":
Code:
$sql = "INSERT INTO userlogging
( ID, date, time, IP, browser, referer )
VALUES ( '', '{$clean['date']}', '{$clean['time']}', '{$clean['ip']}', '{$clean['useragent']}', '{$clean['referer']}' )";