PHP获取上个月、下个月、本月的日期(strtotime(),date())

　　今天写程序的时候，突然发现了很早以前写的获取月份天数的函数，经典的switch版，但是获得上月天数的时候，我只是把月份-1了，估计当时太困了吧，再看到有种毛骨悚然的感觉，本来是想再处理一下的，但是一想肯定还有什么超方便的方法，于是找到了下面这个版本，做了一点小修改。

获取本月日期：

<span 1</span> <span function</span> getMonth(<span $date</span><span ){
</span><span 2</span>     <span $firstday</span> = <span date</span>("Y-m-01",<span strtotime</span>(<span $date</span><span ));
</span><span 3</span>     <span $lastday</span> = <span date</span>("Y-m-d",<span strtotime</span>("<span $firstday</span> +1 month -1 day"<span ));
</span><span 4</span>     <span return</span> <span array</span>(<span $firstday</span>,<span $lastday</span><span );
</span><span 5</span> }

　　$firstday是月份的第一天，假如$date是2014-2这样的话，$firstday就会是2014-02-01，然后根据$firstday加一个月就是2014-03-01，再减一天就是2014-02-28，用date()和strtotime()真是太方便了。

获取上月日期：

<span 1</span> <span function</span> getlastMonthDays(<span $date</span><span ){
</span><span 2</span>     <span $timestamp</span>=<span strtotime</span>(<span $date</span><span );
</span><span 3</span>     <span $firstday</span>=<span date</span>('Y-m-01',<span strtotime</span>(<span date</span>('Y',<span $timestamp</span>).'-'.(<span date</span>('m',<span $timestamp</span>)-1).'-01'<span ));
</span><span 4</span>     <span $lastday</span>=<span date</span>('Y-m-d',<span strtotime</span>("<span $firstday</span> +1 month -1 day"<span ));
</span><span 5</span>     <span return</span> <span array</span>(<span $firstday</span>,<span $lastday</span><span );
</span><span 6</span> }

　　上月日期需要先获取一个时间戳，然后在月份上-1就OK了，超智能的date()会把2014-0-1这种东西转换成2013-12-01，太爽了。

获取下月日期：

<span  1</span> <span function</span> getNextMonthDays(<span $date</span><span ){
</span><span  2</span>     <span $timestamp</span>=<span strtotime</span>(<span $date</span><span );
</span><span  3</span>     <span $arr</span>=<span getdate</span>(<span $timestamp</span><span );
</span><span  4</span>     <span if</span>(<span $arr</span>['mon'] == 12<span ){
</span><span  5</span>         <span $year</span>=<span $arr</span>['year'] +1<span ;
</span><span  6</span>         <span $month</span>=<span $arr</span>['mon'] -11<span ;
</span><span  7</span>         <span $firstday</span>=<span $year</span>.'-0'.<span $month</span>.'-01'<span ;
</span><span  8</span>         <span $lastday</span>=<span date</span>('Y-m-d',<span strtotime</span>("<span $firstday</span> +1 month -1 day"<span ));
</span><span  9</span>     }<span else</span><span {
</span><span 10</span>         <span $firstday</span>=<span date</span>('Y-m-01',<span strtotime</span>(<span date</span>('Y',<span $timestamp</span>).'-'.(<span date</span>('m',<span $timestamp</span>)+1).'-01'<span ));
</span><span 11</span>         <span $lastday</span>=<span date</span>('Y-m-d',<span strtotime</span>("<span $firstday</span> +1 month -1 day"<span ));
</span><span 12</span> <span     }
</span><span 13</span>     <span return</span> <span array</span>(<span $firstday</span>,<span $lastday</span><span );
</span><span 14</span> }

　　下月日期的代码看起来比较长一点，因为date()转不了类似2014-13-01这种东西，它会直接回到1970，所以前面需要处理一下12月的问题，除了12月就直接月份+1就OK啦。

　　总得来说，还是很方便的，日期函数太强大了。