[PHP知识库]PHP获取某月上个月的今天(亲测可用)

    $time = strtotime("2011-03-31"); 
    /**
     * 计算上一个月的今天，如果上个月没有今天，则返回上一个月的最后一天
     * @param type $time
     * @return type
     */      
    function last_month_today($time){ 
        $last_month_time = mktime(date("G", $time), date("i", $time), 
        date("s", $time), date("n", $time), 0, date("Y", $time)); 
        $last_month_t =  date("t", $last_month_time);  //二月份的天数 
		if ($last_month_t < date("j", $time)) { 
            return date("Y-m-t H:i:s", $last_month_time); 
        }  
        return date(date("Y-m", $last_month_time) . "-d", $time); 
    } 

    echo last_month_today($time)."\n"; 
	echo date("H",time()).date("a",time())."\n";
	echo date("Y-m-d",mktime(0,0,0,4,-31,2011))."\n";

//输出结果
2011-02-28 00:00:00
06am
2011-02-28