A detailed explanation of the usage of multi-dimensional arrays in PHP

In PHP development, arrays are a very important data structure, and multidimensional arrays are a more complex array type. As the size and requirements of projects increase, programmers need to use a variety of array structures to meet data processing needs.

Introduction to multidimensional arrays

A multidimensional array simply refers to an array containing multiple one-dimensional arrays. In PHP, the nature of a multidimensional array is recursive, i.e. it can continue to contain multiple nested multidimensional arrays. Unlike regular arrays, the elements in a multidimensional array can be an array (a single value or a collection of multiple values). You need to specify multiple key names to get or set values ​​in a multidimensional array.

In PHP, using arrays to store data is one of the most commonly used methods. Multidimensional arrays are a way to store more complex structured data. Therefore, proficiency in the use of multi-dimensional arrays is very important for processing complex data structures.

Declaring a multidimensional array

Creating a multidimensional array requires the use of multiple array symbols. For example, the following code will create a 2-dimensional array containing nested 1-dimensional arrays:

$scores = array(
    array("Tom", 98),
    array("Jerry", 89),
    array("Spike", 66)
);

The above code stores 3 arrays in the array $scores. Each array contains 2 elements. The first element is A string variable representing the student's name; the second element is an integer variable representing the student's score.

Reading and writing multi-dimensional arrays

To read multi-dimensional array elements, you only need to specify the complete key name. For example, you can use the following code to get Tom's score:

echo $scores[0][1];

In the above code, $scores[0] points to the first array, and [1] points to the second element, which is Tom's score of 98.

Similarly, you can also traverse the array to obtain all student names and scores in the following way:

foreach ($scores as $score) {
    echo $score[0].": ".$score[1]."<br>";
}

The above code will output the following content in sequence:

Tom: 98
Jerry: 89
Spike: 66

Change the multi-dimensional array Values ​​in other internal arrays also need to specify complete key names. For example, the following code will change Jerry's score:

$scores[1][1] = 95;

In the above code, $scores[1] points to the second array, and [1] points to the second element, which is Jerry's score. The code changes Jerry's score from 89 to 95.

Traversing multi-dimensional arrays

There are many ways to traverse multi-dimensional arrays. The following are two of the most common methods.

1. Use a loop to traverse:

$scores = array(
    array("Tom", 98),
    array("Jerry", 89),
    array("Spike", 66)
);

for ($i = 0; $i < count($scores); $i++) {
    for ($j = 0; $j < count($scores[$i]); $j++) {
        echo $scores[$i][$j]." ";
    }
    echo "
";
}

The above code will output the following content in sequence:

Tom 98
Jerry 89
Spike 66

2. Use foreach to traverse:

$scores = array(
    array("Tom", 98),
    array("Jerry", 89),
    array("Spike", 66)
);

foreach ($scores as $score) {
    foreach ($score as $value) {
        echo $value." ";
    }
    echo "
";
}

Above The code will also output the following content:

Tom 98
Jerry 89
Spike 66

Summary

Multidimensional array is a very powerful tool that can help us implement complex data processing operations. Although it is a little complicated, it is very convenient to use as long as you master its basic usage. Whether it is processing financial data or developing games, multidimensional arrays are a very practical function.

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