php时间间隔

/**
 * 用户得到与现在时间的间隔
 * @param type $timestamp
 * @return type
 */
function ago( $timestamp ) {
    $difference = time() - strtotime($timestamp);
    $difference = abs( $difference );
    $periods = array("秒", "分钟", "小时", "天", "星期", "月", "年", "十年");
    $lengths = array("60","60","24","7","4.35","12","10");
    for( $j = 0; $difference >= $lenghts[$j]; $j++ ) {
        $difference = $difference / $lengths[$j];
    }
    $difference = floor($difference);
    $text = "$difference $periods[$j]前";
    return $text;
}