【PHP-日期和时间】时间差异计算函数

function ago($time)
{
    $periods = array("second", "minute", "hour", "day", "week", "month", "year", "decade");
    $lengths = array("60","60","24","7","4.35","12","10");
    $now = time();
    $difference = $now - $time;
    $tense = "ago";
    for($j = 0; $difference >= $lengths[$j] && $j < count($lengths)-1; $j++) {
        $difference /= $lengths[$j];
    }
    $difference = round($difference);
    if($difference != 1) {
        $periods[$j].= "s";
    }
    return "$difference $periods[$j] 'ago' ";
}