How to define multidimensional array in php

PHP is a widely used server-side scripting language. It is widely used in the field of Web development because it is easy to learn and use and supports a variety of databases. Arrays in PHP are one of the most commonly used data types. It allows us to store multiple values ​​in a variable. In actual project development, we often encounter the need to store multiple similar data, such as cities, provinces and other data types. In this case, we need to use multi-dimensional arrays in PHP. This article will introduce how to define multi-dimensional arrays in PHP.

1. What is a multidimensional array

A multidimensional array refers to an array that contains other arrays. In other words, a multidimensional array is an "array collection" composed of a series of single arrays.

Let’s use a specific example to illustrate. For example, we want to save the following student information:

Name: Zhang San
Age: 20
Gender: Male
City: Beijing

Name: Li Si
Age: 21
Gender: Male
City: Shanghai

Name: Wang Wu
Age: 22
Gender: Female
City: Guangzhou

We can define a two-dimensional array$students, where each element is a one-dimensional array to store the information of each student .

2. Define a two-dimensional array

In PHP, we can define a two-dimensional array in the following ways:

// 方法一
$array = array(
    array(1, 2, 3),
    array("name"=>"Tom", "age"=>30),
    array("name"=>"Jerry", "age"=>25),
);

// 方法二
$array[0] = array(1, 2, 3);
$array[1] = array("name"=>"Tom", "age"=>30);
$array[2] = array("name"=>"Jerry", "age"=>25);

In method one, we used ## directly #array() function, with multiple one-dimensional arrays nested in it. In method two, we first define a one-dimensional array, and then instantiate it into two-dimensional arrays one by one.

3. Define a three-dimensional array

If you want to define a three-dimensional array, the method is similar to defining a two-dimensional array. Taking a student grade list as an example, we can define the following three-dimensional array:

$grades = array(
    array(
        array("math"=>90, "english"=>85, "science"=>95),
        array("math"=>85, "english"=>80, "science"=>92),
    ),
    array(
        array("math"=>95, "english"=>92, "science"=>80),
        array("math"=>88, "english"=>90, "science"=>87),
    ),
);

Each element in this array is a two-dimensional array composed of multiple one-dimensional arrays containing subjects and grades. . And each two-dimensional array is a student's transcript.

4. Loop through multi-dimensional arrays

To traverse multi-dimensional arrays, you can use nested

for, foreach, while etc. statements.

Taking a two-dimensional array as an example, we can use the

foreach statement to traverse:

foreach ($students as $student) {
    echo "姓名：". $student['name']. "<br>";
    echo "年龄：". $student['age']. "<br>";
    echo "性别：". $student['gender']. "<br>";
    echo "城市：". $student['city']. "<br>";
    echo "<hr>";
}

For a three-dimensional array, a multi-level loop must be used:

foreach ($grades as $grade) {
    foreach ($grade as $subject) {
        echo "数学成绩：". $subject['math']. "<br>";
        echo "英语成绩：". $subject['english']. "<br>";
        echo "科学成绩：". $subject['science']. "<br>";
        echo "<hr>";
    }
}

5. Summary

This article introduces the definition and traversal method of multi-dimensional arrays in PHP. In practice, we often need to use multi-dimensional arrays to store and process data. Therefore, mastering the definition and basic operations of multi-dimensional arrays will help improve efficiency and quality in projects.

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