function time2Units ($time)
{
		$year   = floor($time / 60 / 60 / 24 / 365);
		$time  -= $year * 60 * 60 * 24 * 365;
		$month  = floor($time / 60 / 60 / 24 / 30);
		$time  -= $month * 60 * 60 * 24 * 30;
		$week   = floor($time / 60 / 60 / 24 / 7);
		$time  -= $week * 60 * 60 * 24 * 7;
		$day    = floor($time / 60 / 60 / 24);
		$time  -= $day * 60 * 60 * 24;
		$hour   = floor($time / 60 / 60);
		$time  -= $hour * 60 * 60;
		$minute = floor($time / 60);
		$time  -= $minute * 60;
		$second = $time;
		$elapse = '';
		
		$unitArr = array('年前'  =>'year', '个月前'=>'month',  '周前'=>'week', '天前'=>'day',
				'小时前'=>'hour', '分钟前'=>'minute', '秒前'=>'second'
		);
		
		foreach ( $unitArr as $cn => $u )
		{
			if ( $year > 0 ) {//大于一年显示年月日
				$elapse = date('Y/m/d',time()-$time);
				break;
			}
			else if ( $$u > 0 )
			{
				$elapse = $$u . $cn;
				break;
			}
		}
		
		return $elapse;
}

$past = 2052345678; //已经过去的时间
$diff = time() - $past;

echo '发表于' . time2Units($diff) . '前';