What does multidimensional array in php mean?

The multi-dimensional array in php refers to the meaning of one or more arrays. For example, a two-dimensional array is a one-dimensional array with multiple one-dimensional arrays defined inside it. The dimensions of the array indicate the index number of the elements you need to select. , for example, a two-dimensional array requires two indexes to select elements, and a three-dimensional array requires three indexes to select elements.

The operating system of this tutorial: Windows10 system, PHP version 8.1.3, DELL G3 computer.

PHP - Multidimensional Array

Multidimensional array refers to an array containing one or more arrays.

PHP can understand multi-dimensional arrays of two, three, four or five levels or even more levels. However, arrays more than three levels deep are difficult for most people to manage.

Note: The dimensions of the array indicate the index number of elements you need to select.

For a two-dimensional array, you need two indexes to select elements

For a three-dimensional array, you need three indexes to select an element

PHP - Two-dimensional array

Two-dimensional arrays are arrays of arrays (three-dimensional arrays are arrays of arrays of arrays).

First, let’s take a look at the table below:

Brand Inventory Sales

Volvo 33 20

BMW 17 15

Saab 5 2  

Land Rover 15 11

We can store the data in the above table in a two-dimensional array, like this:

$cars = array
  (
  array("Volvo",22,18),
  array("BMW",15,13),
  array("Saab",5,2),
  array("Land Rover",17,15)
  );

Now this two-dimensional array contains Four arrays, and it has two indices (subscripts): row and column.

To access an element in the $cars array we must use two indices (row and column):

Example

<?phpheader("Content-type:text/html;charset=utf-8");
$cars = array
   (
   array("Volvo",33,20),
   array("BMW",17,15),
   array("Saab",5,2),
   array("Land Rover",15,11)
   );
   echo $cars[0][0].": 库存：".$cars[0][1].", 已售：".$cars[0][2].".<br>";
   echo $cars[1][0].": 库存：".$cars[1][1].", 已售：".$cars[1][2].".<br>";
   echo $cars[2][0].": 库存：".$cars[2][1].", 已售：".$cars[2][2].".<br>";
   echo $cars[3][0].": 库存：".$cars[3][1].", 已售：".$cars[3][2].".<br>";
   ?>

We can also use another For loop inside the For loop to get the elements in the $cars array (we still need to use two indexes):

<?php
header("Content-type:text/html;charset=utf-8");
$cars = array
   (
   array("Volvo",33,20),
   array("BMW",17,15),
   array("Saab",5,2),
   array("Land Rover",15,11)
   );
   for ($row = 0; $row <  4; $row++) {
   echo "<p><b>行数 $row</b></p>";
   echo "<ul>";
   for ($col = 0; $col <  3; $col++) {
     echo "<li>".$cars[$row][$col]."</li>";
   }
   echo "</ul>";
   }
   ?>

two-dimensional Array creation method:

The two-dimensional array and one-dimensional array are created in the same way, just replace the elements in the array with an array. 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 create and initialize two elements in the format of "$array variable name [row subscript] [column subscript] = value;" Dimensional array

<?php
header("Content-type:text/html;charset=utf-8");
$array[0][&#39;姓名&#39;] = &#39;张三&#39;;
$array[0][&#39;年龄&#39;] = &#39;25&#39;;
$array[0][&#39;性别&#39;] = &#39;男&#39;;
$array[1][&#39;姓名&#39;] = &#39;李四&#39;;
$array[1][&#39;年龄&#39;] = &#39;21&#39;;
$array[1][&#39;性别&#39;] = &#39;男&#39;;
$array[2][&#39;姓名&#39;] = &#39;娜娜&#39;;
$array[2][&#39;年龄&#39;] = &#39;22&#39;;
$array[2][&#39;性别&#39;] = &#39;女&#39;;
var_dump($array);
?>

Output result:

The row subscript and column subscript of the two-dimensional array can be empty (that is, no specific index value is specified) , then the default is a numeric index, and the index value starts from 0 and increases in sequence by default.

Example 1: "Column subscript" is empty

<?phpheader("Content-type:text/html;charset=utf-8");
$array[0][] = &#39;张三&#39;;
$array[0][] = &#39;25&#39;;
$array[0][] = &#39;男&#39;;
$array[1][] = &#39;李四&#39;;
$array[1][] = &#39;21&#39;;
$array[1][] = &#39;男&#39;;
$array[2][] = &#39;娜娜&#39;;
$array[2][] = &#39;22&#39;;
$array[2][] = &#39;女&#39;;
var_dump($array);
?>

Output result:

Example 2: "Row subscript" is Empty

<?php
header("Content-type:text/html;
charset=utf-8");
$array[][&#39;姓名&#39;] = &#39;张三&#39;;
$array[][&#39;年龄&#39;] = &#39;25&#39;;
$array[][&#39;性别&#39;] = &#39;男&#39;;
$array[][&#39;姓名&#39;] = &#39;李四&#39;;
$array[][&#39;年龄&#39;] = &#39;21&#39;;
$array[][&#39;性别&#39;] = &#39;男&#39;;
$array[][&#39;姓名&#39;] = &#39;娜娜&#39;;
$array[][&#39;年龄&#39;] = &#39;22&#39;;
$array[][&#39;性别&#39;] = &#39;女&#39;;
var_dump($array);
?>

Output result:

Example 3: "Row subscript" and "Column subscript" are both empty

<?php
header("Content-type:text/html;charset=utf-8");
$array[][] = &#39;张三&#39;;
$array[][] = &#39;25&#39;;
$array[][] = &#39;男&#39;;
$array[][] = &#39;李四&#39;;
$array[][] = &#39;21&#39;;
$array[][] = &#39;男&#39;;
$array[][] = &#39;娜娜&#39;;
$array[][] = &#39;22&#39;;
$array[][] = &#39;女&#39;;
var_dump($array);
?>

Output result:

#2. Use the array() function

Using the array() function to declare a two-dimensional array is similar to declaring a one-dimensional array.

1) Index array

<?php
header("Content-type:text/html;charset=utf-8");
$array = array(
    array("张三",25,"男"),
    array("李四",21,"男"),
    array("娜娜",22,"女"));
    var_dump($array);
    ?>

Output result:

##2) Associative array

Example 1:

<?php
header("Content-type:text/html;charset=utf-8");
$array = array(
    "学生1"=>array("张三",25,"男"),
    "学生2"=>array("李四",21,"男"),
    "学生3"=>array("娜娜",22,"女"));
    var_dump($array);
    ?>

Output result:

Example 2:

<?php
header("Content-type:text/html;charset=utf-8");
$array = array(
   "学生1"=>array("姓名"=>"张三","年龄"=>25,"性别"=>"男"),   
   "学生2"=>array("姓名"=>"李四","年龄"=>21,"性别"=>"男"),  
   "学生3"=>array("姓名"=>"娜娜","年龄"=>22,"性别"=>"女")); 
   var_dump($array);
   ?>

Output result:

Description: Get the elements in the two-dimensional array

Just indicate the subscript of each dimension

<?php
header("Content-type:text/html;charset=utf-8");
$array = array(
    array("姓名"=>"张三","年龄"=>25,"性别"=>"男"),
    array("姓名"=>"李四","年龄"=>21,"性别"=>"男"),
    array("姓名"=>"娜娜","年龄"=>22,"性别"=>"女"));
 echo $array[0][&#39;姓名&#39;].&#39;同学的年龄为&#39;.$array[0][&#39;年龄&#39;].&#39;岁&#39;;
 ?>

Output result:

<?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);
?>

Output result:

The above is the detailed content of What does multidimensional array in php mean?. For more information, please follow other related articles on the PHP Chinese website!