谨慎使用php的strtotime()函数,phpstrtotime函数_PHP教程
谨慎使用php的strtotime()函数,phpstrtotime函数
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>$val</span>]."\r\n"<span>; </span><span>21</span> }
我们看一下测试结果,从测试结果中,我们发现我们忽略了每个月天数不同,那么strtotime()会带来不一样的结果
那么究竟 strtotime("-$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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