In php how does usort() function works(在 php 中 usort() 函数是如何工作的)

本文介绍了在 php 中 usort() 函数是如何工作的的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我已经查看了 php 文档、在线教程，但没有一个了解 usort 的实际工作方式.我有一个我在下面玩的例子.

I have looked at the php documentation, tutorials online and none of them how usort is actually working. I have an example i was playing with below.

$data = array(

    array('msg' => 'some text','month' => 11,'level' => 10),

    array('msg' => 'some text','month' => 5,'level' => 10),

    array('msg' => 'some text','month' => 8,'level' => 10),

    array('msg' => 'some text','month' => 12,'level' => 10),

    array('msg' => 'some text','month' => 2,'level' => 10),

    array('msg' => 'some text','month' => 3,'level' => 10),

    array('msg' => 'some text','month' => 4,'level' => 10),

    array('msg' => 'some text','month' => 7,'level' => 10),

    array('msg' => 'some text','month' => 10,'level' => 10),

    array('msg' => 'some text','month' => 1,'level' => 10),

    array('msg' => 'some text','month' => 6,'level' => 10),

    array('msg' => 'some text','month' => 9,'level' => 10)

);
我希望能够从 12 到 1 对月份进行排序(因为它们是无组织的)通过一些帮助，这是解决方案 I wanted to be able to sort the months from 12 to 1 (since their unorganized) through some help this was the solution function cmp($a, $b) { if ($a["month"] == $b["month"]) { return 0; } return ($a["month"] < $b["month"]) ? -1 : 1; } usort($data, "cmp"); 但我不明白函数 cmp 如何对数组进行排序.我试着像这样打印出每个变量 $a 和 $b: but i dont understand how the function cmp sorts the array. i tried printing out each variable $a and $b like this: function cmp($a, $b) { echo "a: ".$a['month']."<br/>"; echo " b: ".$b['month']."<br/>"; echo "<br/><br/>"; } 输出为 a: 3 b: 5 a: 9 b: 3 a: 3 b: 8 a: 6 b: 3 a: 3 b: 12 a: 1 b: 3 a: 3 b: 2 a: 10 b: 3 a: 3 b: 11 a: 7 b: 3 a: 4 b: 3 a: 12 b: 2 a: 5 b: 12 a: 12 b: 11 a: 8 b: 12 a: 5 b: 8 a: 2 b: 11 a: 6 b: 9 a: 7 b: 6 a: 6 b: 4 a: 10 b: 6 a: 1 b: 6 a: 9 b: 4 a: 7 b: 1 a: 10 b: 7 排序是如何工作的以及为什么使用 cmp($a, $b) 是没有意义的.正如你所看到的，我试图打印出它的所有流程，但还没有找到任何解决方案来解决它的工作原理.. it makes no sense to how the sort is working and why cmp($a, $b) is used. i have tried to print out all its processes as you can see but have not come to any solution to how it all works.. 谢谢 推荐答案

cmp 函数本身不进行排序.它只是告诉 usort 一个值是否小于、等于或大于另一个值.例如.如果 $a = 5 和 $b = 9 它将返回 1 表示 $b 中的值大于 $b 中的值代码>$a.

The function cmp itself doesn't do the sorting. It just tells usort if a value is smaller, equal or greater than another value. E.g. if $a = 5 and $b = 9 it will return 1 to indicate that the value in $b is greater than the one in $a.

排序由usor完成.

这篇关于在 php 中 usort() 函数是如何工作的的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！