function ago($timestamp)
{
    $difference = time() - $timestamp;

    $periods = array("second", "minute", "hour", "day", "week", "month", "years", "decade");
    $lengths = array("60","60","24","7","4.35","12","10");
    for($j = 0; $difference >= $lengths[$j]; $j++)
    {
        $difference /= $lengths[$j];
    }

    $difference = round($difference);
    if($difference != 1) $periods[$j].= "s";

    $text = "$difference $periods[$j] ago";
    return $text;
}