Analysis of multi-dimensional array sorting algorithm implemented in PHP

The example in this article describes the multi-dimensional array sorting algorithm implemented in PHP. Share it with everyone for your reference, the details are as follows:

Suddenly I remembered an interview question, sorting a multi-dimensional array.

Example:

<?php
//有一个多维数组
$a = array(
  array(&#39;key1&#39;=>940, &#39;key2&#39;=>&#39;blah&#39;),
  array(&#39;key1&#39;=>23, &#39;key2&#39;=>&#39;this&#39;),
  array(&#39;key1&#39;=>894, &#39;key2&#39;=>&#39;that&#39;)
);
//那么怎么对key1或者key2进行排序呢,这里就需要使用到usort($arr, &#39;myfunction&#39;)函数了，它的作用是对$arr使用我们自定义的方法进行排序，具体使用方法可以查看手册
//1.对key1的值进行排序
function asc_key1_sort($x, $y) {
  //可以输出一下看看是怎么比较的
  echo &#39;Iteration:&#39;.$x[&#39;key1&#39;].&#39; vs &#39;.$y[&#39;key1&#39;];
  if($x[&#39;key1&#39;] > $y[&#39;key1&#39;]) {
    echo &#39;true<br/>&#39;;
    return true;
  }elseif($x[&#39;key1&#39;] < $y[&#39;key1&#39;]) {
    echo &#39;false<br/>&#39;;
    return false;
  }else {
    echo &#39;0&#39;;
    return 0;
  }
}
//进行排序
usort($a, &#39;asc_key1_sort&#39;);
var_dump($a);
//2.对key2字符进行排序
function asc_key2_sort($x, $y) {
  //可以使用strcasecmp()函数进行排序
  echo &#39;Iteration:&#39;.$x[&#39;key2&#39;].&#39; vs &#39;.$y[&#39;key2&#39;].&#39;<br/>&#39;;
  return strcasecmp($x[&#39;key2&#39;], $y[&#39;key2&#39;]);
}
//进行排序
usort($a, &#39;asc_key2_sort&#39;);
var_dump($a);
?>

Running result:

Iteration:23 vs 940false
Iteration:894 vs 23true
Iteration:940 vs 23true
Iteration:894 vs 940false
array(3) { [0]=> array(2) { ["key1"]=> int(23) ["key2"]=> string(4) "this" } [1]=> array(2) { ["key1"]=> int(894) ["key2"]=> string(4) "that" } [2]=> array(2) { ["key1"]=> int(940) ["key2"]=> string(4) "blah" } } Iteration:that vs this
Iteration:blah vs that
array(3) { [0]=> array(2) { ["key1"]=> int(940) ["key2"]=> string(4) "blah" } [1]=> array(2) { ["key1"]=> int(894) ["key2"]=> string(4) "that" } [2]=> array(2) { ["key1"]=> int(23) ["key2"]=> string(4) "this" } }

What if my multidimensional array also has key values?

<?php
//有一个多维数组
$a = array(
  123 => array(&#39;key1&#39;=>940, &#39;key2&#39;=>&#39;blah&#39;),
  349 => array(&#39;key1&#39;=>23, &#39;key2&#39;=>&#39;this&#39;),
  43 => array(&#39;key1&#39;=>894, &#39;key2&#39;=>&#39;that&#39;)
);
//那么怎么对key1或者key2进行排序呢,这里就需要使用到usort($arr, &#39;myfunction&#39;)函数了，它的作用是对$arr使用我们自定义的方法进行排序，具体使用方法可以查看手册
//1.对key1的值进行排序
function asc_key1_sort($x, $y) {
  //可以输出一下看看是怎么比较的
  echo &#39;Iteration:&#39;.$x[&#39;key1&#39;].&#39; vs &#39;.$y[&#39;key1&#39;];
  if($x[&#39;key1&#39;] > $y[&#39;key1&#39;]) {
    echo &#39;true<br/>&#39;;
    return true;
  }elseif($x[&#39;key1&#39;] < $y[&#39;key1&#39;]) {
    echo &#39;false<br/>&#39;;
    return false;
  }else {
    echo &#39;0&#39;;
    return 0;
  }
}
//进行排序
usort($a, &#39;asc_key1_sort&#39;);
var_dump($a);
//2.对key2字符进行排序
function asc_key2_sort($x, $y) {
  //可以使用strcasecmp()函数进行排序
  echo &#39;Iteration:&#39;.$x[&#39;key2&#39;].&#39; vs &#39;.$y[&#39;key2&#39;].&#39;<br/>&#39;;
  return strcasecmp($x[&#39;key2&#39;], $y[&#39;key2&#39;]);
}
//进行排序
usort($a, &#39;asc_key2_sort&#39;);
var_dump($a);
?>

Running result:

Iteration:23 vs 940false
Iteration:894 vs 23true
Iteration:940 vs 23true
Iteration:894 vs 940false
array(3) { [0]=> array(2) { ["key1"]=> int(23) ["key2"]=> string(4) "this" } [1]=> array(2) { ["key1"]=> int(894) ["key2"]=> string(4) "that" } [2]=> array(2) { ["key1"]=> int(940) ["key2"]=> string(4) "blah" } } Iteration:that vs this
Iteration:blah vs that
array(3) { [0]=> array(2) { ["key1"]=> int(940) ["key2"]=> string(4) "blah" } [1]=> array(2) { ["key1"]=> int(894) ["key2"]=> string(4) "that" } [2]=> array(2) { ["key1"]=> int(23) ["key2"]=> string(4) "this" } }

Such a sorting result will not retain 123, 349, 43. At this time, just replace usort() with uasort!

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