How to define a multidimensional array and obtain its elements in PHP?

In the previous article, I brought you "Take you through PHP filters in three minutes (detailed examples)", which introduced the relevant knowledge of PHP filters in detail. In this article, we Let’s take a look at the knowledge related to multi-dimensional arrays in PHP. I hope it will be helpful to everyone!

Through the previous study, we know that arrays in PHP can store all types of data, including of course the array itself. At this time, when the elements in one array are another array, what should we call the array that constitutes the containing array? When the elements in the contained array are still an array, how should we deal with it?

An array is simply a number or a simple list. Sometimes we want to use more than one key to save data. In this case, we need to use the included key we just mentioned. Array, this is called a multi-dimensional array. Next, let’s take a look at the relevant knowledge of multi-dimensional arrays.

Two-dimensional array

As we said above, when the elements in one array are another array, this The arrays that constitute the package function group are two-dimensional arrays, and two-dimensional arrays are simply understood as arrays of arrays. Is its declaration method any different from that of an ordinary array?

The declaration method of two-dimensional array and one-dimensional array is the same, except that one or more elements in the array are also declared as an array. At the same time, there are also direct assignment and use of array elements. The array() function has two ways of declaring a two-dimensional array.

Let's take an example to declare an array by directly assigning values ​​​​to the array elements. The example is as follows:

<?php
    $array[0][&#39;name&#39;] = &#39;father&#39;;
    $array[0][&#39;year&#39;] = &#39;1949&#39;;
    $array[0][&#39;age&#39;] = &#39;72&#39;;
    $array[1][&#39;name&#39;] = &#39;mother&#39;;
    $array[1][&#39;year&#39;] = &#39;1949&#39;;
    $array[1][&#39;age&#39;] = &#39;72&#39;;
    echo &#39;<pre class="brush:php;toolbar:false">&#39;;
    print_r($array);
?>

Output result:

In the above example, an array is declared by directly assigning values ​​to the array elements. Next, let’s look at declaring a two-dimensional array through the array() function. In the case of arrays, the example is as follows:

<?php
    $array = array(
        array(&#39;name&#39;=>&#39;father&#39;,&#39;year&#39;=>&#39;1949&#39;,&#39;age&#39;=>&#39;72&#39;),
        array(&#39;name&#39;=>&#39;mother&#39;,&#39;year&#39;=>&#39;1949&#39;,&#39;age&#39;=>&#39;72&#39;)
    );
    echo &#39;<pre class="brush:php;toolbar:false">&#39;;
    print_r($array);
?>

The output result is consistent with the output result in the above example.

After declaring a two-digit array, it is very simple to obtain the elements. It is similar to a one-dimensional array. You only need to indicate the subscript of each dimension.

Next, let’s look at how to get the elements in the two-digit array through an example. The example is as follows:

<?php
    $array = array(
        array(&#39;name&#39;=>&#39;father&#39;,&#39;year&#39;=>&#39;1949&#39;,&#39;age&#39;=>&#39;72&#39;),
        array(&#39;name&#39;=>&#39;mother&#39;,&#39;year&#39;=>&#39;1949&#39;,&#39;age&#39;=>&#39;72&#39;)
    );
    echo &#39;<pre class="brush:php;toolbar:false">&#39;;
    print_r($array);
    echo $array[0][&#39;name&#39;].&#39;在&#39;.$array[0][&#39;year&#39;].&#39;年出生，今年已经&#39;.$array[0][&#39;age&#39;].&#39;岁了<br/>&#39;;
    echo $array[1][&#39;name&#39;].&#39;在&#39;.$array[1][&#39;year&#39;].&#39;年出生，今年已经&#39;.$array[1][&#39;age&#39;].&#39;岁了&#39;;
?>

Output result:

What we need to pay attention to is: the different dimensions of the array indicate that we need to use several subscripts to get the corresponding array elements. For example, a two-dimensional array needs to use two subscripts to get the corresponding array elements, a three-dimensional array requires three, and so on.

Sometimes we want to use more than one key to save data, so we need to use PHP's multi-dimensional array to achieve it. However, sometimes you want to store values ​​with more than one key. At this time, you can use multi-dimensional arrays for storage. Next let's take a look at multidimensional arrays.

Multi-dimensional array

In addition to two-dimensional arrays, PHP also supports three-dimensional arrays, four-dimensional arrays and even more multi-dimensional arrays, which can be collectively referred to here It is a multi-dimensional array, but when the array exceeds three dimensions, its readability will be greatly reduced, and it will not be easy to manage.

Refer to the two-dimensional array and draw inferences. You can easily create a three-dimensional array, a four-dimensional array, or other higher-dimensional arrays. Next, let’s take a look at how a three-dimensional array is defined through an example. The example is as follows:

<?php
    $arr = array(
        &#39;中国&#39; => array(
            &#39;安徽&#39;=>array(&#39;合肥&#39;,&#39;蚌埠&#39;,&#39;芜湖&#39;),
            &#39;江苏&#39;=>array(&#39;南京&#39;,&#39;徐州&#39;,&#39;苏州&#39;),
            &#39;浙江&#39;=>array(&#39;杭州&#39;,&#39;宁波&#39;,&#39;温州&#39;)
        ),
        &#39;美国&#39; => array(
            &#39;阿拉斯加州&#39;=>array(&#39;朱诺&#39;,&#39;安克雷奇&#39;),
            &#39;路易斯安那州&#39;=>array(&#39;新奥尔良&#39;,&#39;巴吞鲁日&#39;),
            &#39;加利福尼亚州&#39;=>array(&#39;洛杉矶&#39;,&#39;萨克拉门托&#39;)
        )
    );
echo &#39;<pre class="brush:php;toolbar:false">&#39;;
    print_r($arr);
    echo $arr[&#39;中国&#39;][&#39;安徽&#39;][0];  // 输出合肥
?>

Output result:

The above example is The definition of multidimensional arrays and how to obtain elements in multidimensional arrays.

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