将时间转成几天前，几小时等的格式，如： “1天前”，“2个月前”等。

 <?php
function prettyDate($date){
    $time = strtotime($date);
    $now = time();
    $ago = $now - $time;
    if($ago < 60){
        $when = round($ago);
        $s = ($when == 1)?"second":"seconds";
        return "$when $s ago";
    }elseif($ago < 3600){
        $when = round($ago / 60);
        $m = ($when == 1)?"minute":"minutes";
        return "$when $m ago";
    }elseif($ago >= 3600 && $ago < 86400){
        $when = round($ago / 60 / 60);
        $h = ($when == 1)?"hour":"hours";
        return "$when $h ago";
    }elseif($ago >= 86400 && $ago < 2629743.83){
        $when = round($ago / 60 / 60 / 24);
        $d = ($when == 1)?"day":"days";
        return "$when $d ago";
    }elseif($ago >= 2629743.83 && $ago < 31556926){
        $when = round($ago / 60 / 60 / 24 / 30.4375);
        $m = ($when == 1)?"month":"months";
        return "$when $m ago";
    }else{
        $when = round($ago / 60 / 60 / 24 / 365);
        $y = ($when == 1)?"year":"years";
        return "$when $y ago";
    }
}

echo prettyDate("2012-07-22 12:23:45")."<br />";
echo prettyDate("2010-11-12 22:25:45")."<br />";
echo prettyDate("2012-01-01 01:00:00")."<br />";
echo prettyDate("2001-05-30 00:00:00")."<br />";