我们在日常业务中，针对业务量，经常会采用对数据库按时间做横向分表，分表后的查询往往会涉及到时间问题。例如，我们想查询某个用户距离当前时间1个月的订单情况，在这个时候，我们有些会用到strtotime()函数去处理。
但是使用strtotime()，需要非常谨慎。我们先看一段代码，代码目的是想拿到几个月以前的年份月份，例如今天是2014年8月1号，我想拿到2个月前的年份月份是 array("0"=>"201406", "1"=>"201407",)
<span> 1</span> <span>/*</span><span>***
</span><span> 2</span> <span>*$mthNum 几月以前
</span><span> 3</span> <span>* return like array('0'=>'201401','1'=>'201402')，结果不包含当前月份
</span><span> 4</span> <span>***********</span><span>*/</span>
<span> 5</span> <span>function</span> getTimeYm(<span>$mthNum</span><span>)
</span><span> 6</span> <span>{
</span><span> 7</span> <span>$timeArr</span> = <span>array</span><span>();
</span><span> 8</span>
<span> 9</span> <span>if</span>(<span>$mthNum</span> <= 0<span>)
</span><span>10</span> <span>return</span> <span>$timeArr</span><span>;
</span><span>11</span>
<span>12</span> <span>do</span>
<span>13</span> <span> {
</span><span>14</span> <span>$timeArr</span>[] = <span>date</span>("Ym", <span>strtotime</span>("-<span>$mthNum</span> month"<span>));
</span><span>15</span> <span>$mthNum</span> --<span>;
</span><span>16</span> <span> }
</span><span>17</span> <span>while</span> (<span>$mthNum</span> > 0<span>);
</span><span>18</span>
<span>19</span> <span>return</span> <span>$timeArr</span><span>;
</span><span>20</span> }
表面看代码似乎没有问题，但是我们做个测试，下面是测试代码，测试的目的很简单，只是想测试一下，每个月最后一天的前一个月的日期是多少
<span> 1</span> <?<span>php
</span><span> 2</span> <span>$dateArr</span> = <span>array</span><span>(
</span><span> 3</span> "2014-01-31 00:00:00 -1 month",
<span> 4</span> "2014-02-28 00:00:00 -1 month",
<span> 5</span> "2014-03-31 00:00:00 -1 month",
<span> 6</span> "2014-04-30 00:00:00 -1 month",
<span> 7</span> "2014-05-31 00:00:00 -1 month",
<span> 8</span> "2014-06-30 00:00:00 -1 month",
<span> 9</span> "2014-07-31 00:00:00 -1 month",
<span>10</span> "2014-08-31 00:00:00 -1 month",
<span>11</span> "2014-09-30 00:00:00 -1 month",
<span>12</span> "2014-10-31 00:00:00 -1 month",
<span>13</span> "2014-11-30 00:00:00 -1 month",
<span>14</span> "2014-12-31 00:00:00 -1 month",
<span>15</span> <span>);
</span><span>16</span>
<span>17</span> <span>foreach</span> (<span>$dateArr</span> <span>as</span> <span>$val</span><span>)
</span><span>18</span> <span>{
</span><span>19</span> <span>$time</span> = <span>strtotime</span>(<span>$val</span><span>);
</span><span>20</span> <span>echo</span> [<span>$time</span>][<span>$val</span>]."\r\n"<span>;
</span><span>21</span> } 我们看一下测试结果，从测试结果中，我们发现我们忽略了每个月天数不同，那么strtotime()会带来不一样的结果
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那么究竟 strtotime("-$n month") 是怎么计算的呢？在做一个测试，如下：查看一下结果
<span> 1</span> <?<span>php
</span><span> 2</span>
<span> 3</span> <span>$testTime</span> = <span>date</span>("Y-m-d H:i:s", <span>time</span><span>());
</span><span> 4</span> <span>echo</span> "测试时间：{<span>$testTime</span>} \r\n"<span>;
</span><span> 5</span>
<span> 6</span> <span>$flag</span> = 0<span>;
</span><span> 7</span> <span>$time</span> = 0<span>;
</span><span> 8</span> <span>$tmp</span> = 0<span>;
</span><span> 9</span>
<span>10</span> <span>while</span>(1<span>)
</span><span>11</span> <span>{
</span><span>12</span> <span>if</span>(<span>$flag</span> ++ > 12<span>)
</span><span>13</span> <span>break</span><span>;
</span><span>14</span>
<span>15</span> <span>$time</span> = <span>strtotime</span>("-<span>$flag</span> month"<span>);
</span><span>16</span> <span>$monthDiff</span> = (<span>$time</span> - <span>$tmp</span>)/86400; <span>//</span><span>86400 = 24 * 60 * 60,</span>
<span>17</span> <span>$tmp</span> = <span>$time</span><span>;
</span><span>18</span>
<span>19</span> <span>$dispDate</span> = <span>date</span>("Y-m-d H:i:s", <span>$time</span><span>);
</span><span>20</span>
<span>21</span> <span>echo</span> "{<span>$flag</span>}月前: {<span>$time</span>}, 日期：{<span>$dispDate</span>)} 差值：{<span>$dispDate</span>}天 \r\n"<span>;
</span><span>22</span> }
(注：strtotime("-$n month")，第二个参数省略，第二个参数表示距离的时间，省略表示当前时间)
|
时间 |
差值 |
理论时间 |
结果 |
|
7月31号 |
1月前 |
6月31号 |
6月只有30天，则加一天到7月1号 |
|
7月31号 |
2月前 |
5月31号 |
|
|
7月31号 |
3月前 |
4月31号 |
4月只有30天，则加一天到5月1号 |
|
…… |
|||
那么如果这样的话，我们怎么用strtotime("-$n month")处理我们的需求呢？
下面提供一段手写代码供参考
<span> 1</span> <span>/*</span><span>***************
</span><span> 2</span> <span>*解决两个时间段之间的年月
</span><span> 3</span> <span>* $btm, $etm 是unix时间戳
</span><span> 4</span> <span>****************</span><span>*/</span>
<span> 5</span> <span>function</span> getTimeDis(<span>$btm</span>, <span>$etm</span><span>)
</span><span> 6</span> <span>{
</span><span> 7</span> <span>$resArr</span> = <span>array</span><span>();
</span><span> 8</span> <span>if</span>(<span>$etm</span> < <span>$btm</span><span>)
</span><span> 9</span> <span>return</span> <span>$resArr</span><span>;
</span><span>10</span>
<span>11</span> <span>//</span><span>将btm和etm都转成每月1号</span>
<span>12</span> <span>$btmc</span> = <span>strtotime</span>(<span>date</span>("Y-m-01 00:00:00", <span>$btm</span><span>));
</span><span>13</span> <span>$etmc</span> = <span>strtotime</span>(<span>date</span>("Y-m-01 00:00:00", <span>$etm</span><span>));
</span><span>14</span>
<span>15</span>
<span>16</span> <span>$flag</span> = 0; <span>//</span><span>时间差标识符</span>
<span>17</span> <span>$resArr</span>[] = <span>date</span>("Ym", <span>$etmc</span><span>);
</span><span>18</span>
<span>19</span> <span>while</span>(1<span>)
</span><span>20</span> <span> {
</span><span>21</span> <span>$flag</span> ++<span>;
</span><span>22</span> <span>$compTime</span> = <span>strtotime</span>("-{<span>$flag</span>} month", <span>$etmc</span><span>);
</span><span>23</span>
<span>24</span> <span>if</span>(<span>$compTime</span> < <span>$btm</span><span>)
</span><span>25</span> <span>break</span><span>;
</span><span>26</span>
<span>27</span> <span>$resArr</span>[] = <span>date</span>("Ym", <span>$compTime</span><span>);
</span><span>28</span> <span> }
</span><span>29</span>
<span>30</span> <span>return</span> <span>array_unique</span>(<span>$resArr</span><span>);
</span><span>31</span> }
mktime() 需要带参数的。
想要得到两天后的最简单方法是：
echo date("Y-m-d",strtotime("+2 days"));
echo '
';
echo date("Y-m-d H:i:s",strtotime("+2 days"));
?>
好好看看 strtotime的函数说明，你还可以
+10 hours
-2 hours
等等。
$date = date("Y-m-d", strtotime('2012-01-20') + 60*60*24);
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