How to create a two-dimensional array in php

PHP is a widely used server-side scripting language that can store and manipulate data through arrays. In PHP, an array is an ordered list of elements, each element can be identified by a unique key (also called a subscript). PHP supports one-dimensional arrays and multi-dimensional arrays, of which two-dimensional arrays are the most common type of multi-dimensional arrays. This article will introduce how to build a two-dimensional array in PHP.

1. The concept of two-dimensional array

In PHP, a two-dimensional array is an array, and each element of this array is also an array, that is, each element can contain multiple values. . Two-dimensional arrays are usually used to represent data structures such as tables and matrices.

For example, a two-dimensional array that stores student grades can be defined as follows:

$grades = array(
    array('Alice', 85, 90),
    array('Bob', 76, 80),
    array('Chris', 92, 95)
);

This two-dimensional array contains three elements, each element is also an array, and the first element is the student In the name, the second element is the Chinese score, and the third element is the math score.

2. Creation of a two-dimensional array

In PHP, there are many ways to create a two-dimensional array, including:

1. Manual creation

Manually creating a two-dimensional array requires using a nested array:

$grades = array(
    array('Alice', 85, 90),
    array('Bob', 76, 80),
    array('Chris', 92, 95)
);

Note that the number of elements in each sub-array must be the same, otherwise an error will occur.

2. Dynamic creation

Dynamic creation of a two-dimensional array can be achieved by loop nesting:

$grades = array();
for ($i = 0; $i <p>In this example, a for loop is used to create A two-dimensional array containing 3 elements. Each element is an array containing 3 values. The first value is the student's number, and the next two values ​​are randomly generated grades. </p><ol start="3"><li>Convert a one-dimensional array to a two-dimensional array</li></ol><p>If you already have a one-dimensional array, you can also convert it to a two-dimensional array. For example, there is already a one-dimensional array that stores students' names, Chinese scores, and math scores: </p><pre class="brush:php;toolbar:false">$students = array('Alice', 85, 90, 'Bob', 76, 80, 'Chris', 92, 95);

It can be converted into a two-dimensional array through a loop:

$grades = array();
$count = count($students);
for ($i = 0; $i <p>In this example, $count The variable is used to store the number of elements in the one-dimensional array. The loop takes out three elements each time, creates an array containing three values, and adds it to the two-dimensional array. </p><p>3. Access and operation of two-dimensional arrays</p><p>You need to use two subscripts to access the elements of a two-dimensional array, for example: </p><pre class="brush:php;toolbar:false">echo $grades[1][0]; // 输出 Bob
echo $grades[2][2]; // 输出 95

You can traverse the two-dimensional array by looping All elements, for example:

foreach ($grades as $row) {
    foreach ($row as $grade) {
        echo $grade . ' ';
    }
    echo '<br>';
}

In this example, the outer foreach loop traverses each row, and the inner foreach loop traverses each column, and outputs each element and a newline character.

Two-dimensional arrays also support other common operations, such as adding, deleting, sorting, etc. For specific operations, please refer to the PHP manual.

Summary

This article introduces how to build a two-dimensional array in PHP, including manual creation, dynamic creation, and conversion of one-dimensional arrays to two-dimensional arrays. It also explains how to access and manipulate the elements of a two-dimensional array. Mastering the use of two-dimensional arrays can easily handle complex data structures and improve the efficiency and quality of PHP programming.

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