1 /****
 2 *$mthNum 几月以前
 3 * return like array('0'=>'201401','1'=>'201402')，结果不包含当前月份
 4 ************/
 5 function getTimeYm($mthNum)
 6 {
 7     $timeArr = array();
 8     
 9     if($mthNum <= 0)
10         return $timeArr;
11 
12     do 
13     {
14         $timeArr[] = date("Ym", strtotime("-$mthNum month"));
15         $mthNum --;
16     }
17     while ($mthNum > 0);
18 
19     return $timeArr;
20 }

 1 <?php
 2 $dateArr = array(
 3     "2014-01-31    00:00:00 -1 month",
 4     "2014-02-28    00:00:00 -1 month",
 5     "2014-03-31    00:00:00 -1 month",
 6     "2014-04-30    00:00:00 -1 month",
 7     "2014-05-31    00:00:00 -1 month",
 8     "2014-06-30    00:00:00 -1 month",
 9     "2014-07-31    00:00:00 -1 month",
10     "2014-08-31    00:00:00 -1 month",
11     "2014-09-30    00:00:00 -1 month",
12     "2014-10-31    00:00:00 -1 month",
13     "2014-11-30    00:00:00 -1 month",
14     "2014-12-31    00:00:00 -1 month",
15 );
16 
17 foreach ($dateArr as $val)
18 {
19     $time = strtotime($val);
20     echo [$time][$val]."\r\n";
21 }　　

 1 <?php
 2 
 3 $testTime = date("Y-m-d H:i:s", time());
 4 echo "测试时间：{$testTime}  \r\n";
 5 
 6 $flag = 0; 
 7 $time = 0;
 8 $tmp  = 0;
 9 
10 while(1)
11 {
12     if($flag ++ > 12)
13         break;
14 
15     $time      =  strtotime("-$flag month");
16     $monthDiff = ($time - $tmp)/86400;  //86400 = 24 * 60 * 60,
17     $tmp       = $time;
18 
19     $dispDate = date("Y-m-d H:i:s", $time);
20 
21     echo "{$flag}月前: {$time},  日期：{$dispDate)}   差值：{$dispDate}天 \r\n";
22 }

 1 /****************
 2 *解决两个时间段之间的年月
 3 * $btm, $etm 是unix时间戳
 4 *****************/
 5 function getTimeDis($btm, $etm)
 6 {
 7     $resArr = array();
 8     if($etm < $btm)
 9         return $resArr;
10 
11     //将btm和etm都转成每月1号
12     $btmc = strtotime(date("Y-m-01 00:00:00", $btm));
13     $etmc = strtotime(date("Y-m-01 00:00:00", $etm));
14 
15 
16     $flag = 0; //时间差标识符
17     $resArr[] = date("Ym", $etmc);
18 
19     while(1)
20     {
21         $flag ++;
22         $compTime = strtotime("-{$flag} month",  $etmc);
23         
24         if($compTime < $btm)
25             break;
26 
27         $resArr[] = date("Ym", $compTime);
28     }
29 
30     return array_unique($resArr);
31 }