排序使用PHP多维数组
问题描述：
我要寻找排序多维数组的最佳方式，我希望它基于什么孩子数组包含排序。
I am looking for the best way to sort a multidimensional array, I want it sorted based on what the child array contains.
这是我的数组：
Array
(
[0] => Array
(
[id] => 2
[level] => 3
[lastAction] => "String Here"
[actionAt] => 23/03/2014
)
[1] => Array
(
[id] => 4
[level] => 5
[lastAction] => "Another String here"
[actionAt] => 24/3/2014
)
[2] => Array
(
[id] => 9
[level] => 1
[lastAction] => "String again"
[actionAt] => 01/01/2013
)
)
和我想基础上，从ActionAt他们的孩子阵列中的3个主要数组排序，这怎么可能？
And I would like to sort the 3 main arrays based on the ActionAt from their child arrays, how is this possible?
我读过一些关于它有的说ksort和usort，但我一直没能得到它正常工作。
I've read a bit about it and some say ksort and usort, but I have not been able to get it working properly.
答
您将需要实现自己的比较函数，并使用usort：
You will need to implement your own comparison function and use usort:
function cmp($a, $b)
{
if ($a['actionAt'] == $b['actionAt']) {
return 0;
}
//Assuming your dates are strings (http://stackoverflow.com/questions/2891937/strtotime-doesnt-work-with-dd-mm-yyyy-format)
$atime = strtotime(str_replace('/', '-', $a['actionAt']));
$btime = strtotime(str_replace('/', '-', $b['actionAt']));
return ($atime < $btime) ? -1 : 1;
}
usort($array, "cmp");