What does php three-dimensional array mean?

In PHP, a three-dimensional array refers to an array structure with three dimensions, that is, the elements in the main array are one or more arrays, and the elements in the sub-array are also one or more arrays. Methods to define a three-dimensional array: 1. Directly assign values ​​to the array elements with the syntax "$array variable name [one-dimensional subscript] [two-dimensional subscript] [three-dimensional subscript] = value;"; 2. Use the array() function to define , the syntax "array(key name=>array(key name=>array(key name=>key value, key name=>key value....),...),...); ".

The operating environment of this tutorial: windows7 system, PHP8 version, DELL G3 computer

In PHP, a multi-dimensional array contains one or more An array of arrays, where a three-dimensional array refers to an array structure with three dimensions.

In a three-dimensional array, the elements in the main array are one or more arrays, and the elements in the subarray are also one or more arrays.

Three-dimensional arrays are created in the same way as one-dimensional arrays and two-dimensional arrays, just replace the elements in the array with arrays. There are also two methods: "directly assigning values ​​to array elements" and "array() function". Below we will introduce these two methods in detail with our actual code examples.

1. Directly assign values ​​to array elements

We can pass the format of "$array variable name [one-dimensional subscript] [two-dimensional subscript] [Three-dimensional subscript]=value;" format to create and initialize the three-dimensional array

<?php
header("Content-type:text/html;charset=utf-8");
$array[&#39;安徽&#39;][&#39;合肥&#39;][0] = &#39;蜀山区&#39;;
$array[&#39;安徽&#39;][&#39;合肥&#39;][1] = &#39;长丰县&#39;;
$array[&#39;安徽&#39;][&#39;合肥&#39;][2] = &#39;肥东&#39;;

$array[&#39;安徽&#39;][&#39;宿州&#39;][0] = &#39;墉桥区&#39;;
$array[&#39;安徽&#39;][&#39;宿州&#39;][1] = &#39;灵璧县&#39;;
$array[&#39;安徽&#39;][&#39;宿州&#39;][2] = &#39;泗县&#39;;
var_dump($array);
?>

One-dimensional subscript, two-dimensional subscript and three-dimensional subscript of the three-dimensional array The subscript can be empty (that is, no specific index value is specified), then the default is a numeric index, and the index value increases sequentially starting from 0 by default.

<?php
header("Content-type:text/html;charset=utf-8");
$array[&#39;安徽&#39;][][0] = &#39;蜀山区&#39;;
$array[&#39;安徽&#39;][][1] = &#39;长丰县&#39;;
$array[&#39;安徽&#39;][][2] = &#39;肥东&#39;;

$array[&#39;安徽&#39;][&#39;宿州&#39;][] = &#39;墉桥区&#39;;
$array[&#39;安徽&#39;][&#39;宿州&#39;][] = &#39;灵璧县&#39;;
$array[&#39;安徽&#39;][&#39;宿州&#39;][] = &#39;泗县&#39;;
var_dump($array);
?>

2. Use the array() function

Use the array() function to declare a three-dimensional array and a two-dimensional array. Dimensional arrays are similar.

<?php
header("Content-type:text/html;charset=utf-8");
$array = array(
        &#39;安徽&#39; => array(
            &#39;合肥&#39;=>array(&#39;蜀山区&#39;,&#39;长丰县&#39;,&#39;肥东&#39;),
			&#39;宿州&#39;=>array(&#39;墉桥区&#39;,&#39;灵璧县&#39;,&#39;泗县&#39;)
        ),
        &#39;河南&#39; => array(
            &#39;洛阳&#39;=>array(&#39;西工区&#39;,&#39;老城区&#39;,&#39;孟津县&#39;),
            &#39;郑州市&#39;=>array(&#39;中原区&#39;,&#39;金水区&#39;)
        )
);
 var_dump($array);
?>

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