How to understand foreach traversing a two-dimensional array in php

phpIt is often necessary to use the traversal of two-dimensional array. Many people understand the traversal of one-dimensional array, but for the traversal of two-dimensional array The understanding of traversal means there is nothing you can do. This article will take you to take a look at it.

First of all, if you want to understand the traversal of a two-dimensional array, you must first understand the principle of traversal of a one-dimensional array. Without further ado, let’s go directly to the code.

Two ways to traverse a one-dimensional array:

1. Need to operate on the keys and values ​​of the array

<?php
$arr=array(&#39;a&#39;=>&#39;php&#39;,&#39;c&#39;=>&#39;.cn&#39;);
foreach($arr as $key=>$value){
    echo $key.&#39;=>&#39;.$value."<br>";
}

输出：a=>php
      c=>.cn

2. Need to operate on the keys and values ​​of the array Operation

<?php
$arr2=array(&#39;d&#39;=>&#39;ok&#39;,&#39;b&#39;=>&#39;oya&#39;);
foreach($arr2 as $value){
    echo $value."<br>";
}

输出：  ok
        oya

The traversal of a one-dimensional array is actually the internal pointer of foreach constantly pointing to the next key-value pair. If the pointer is empty, it is restored to the original pointer. Every time you point to a key-value pair, you can operate on the key-value pair inside foreach.

Then let’s take a look at the traversal of the two-dimensional array:

<?php
$arr3=[[3,0,9],[7,8,3],[1,8,2]];
foreach($arr3 as $key=>$value){
    foreach($value as $k=>$v){
        echo &#39;这是二维数组中索引为：&#39;.$key.&#39;的一维数组的第&#39;.$k.&#39;个，值为:&#39;.$v.&#39;<br>&#39;;
    }
    echo "<br>";
}
?>

输出：
这是二维数组中索引为：0的一维数组的第0个，值为:3
这是二维数组中索引为：0的一维数组的第1个，值为:0
这是二维数组中索引为：0的一维数组的第2个，值为:9

这是二维数组中索引为：1的一维数组的第0个，值为:7
这是二维数组中索引为：1的一维数组的第1个，值为:8
这是二维数组中索引为：1的一维数组的第2个，值为:3

这是二维数组中索引为：2的一维数组的第0个，值为:1
这是二维数组中索引为：2的一维数组的第1个，值为:8
这是二维数组中索引为：2的一维数组的第2个，值为:2

In fact, the traversal of the two-dimensional array is to treat the array inside the two-dimensional array as a Variable, use foreach() again to traverse the array we treat as a variable.

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