PHP two-dimensional array to one-dimensional number

PHP is a popular scripting language widely used in web development, especially back-end development. In PHP development, array is a very common data type. During the development process, sometimes you need to convert a two-dimensional array into a one-dimensional array, which is also a basic array operation skill. In this article, I will explain how to convert a 2D array to a 1D array using PHP.

1. What is a two-dimensional array?

In PHP, an array is an ordered collection of elements. Each element has a unique key (key) that can be used to access the element. A two-dimensional array refers to one or more arrays nested within an array. These nested arrays can be arrays of the same type or arrays of different types. In PHP, nested arrays can be used to represent multidimensional data structures, such as matrices, trees, etc.

The following is an example two-dimensional array:

$students = array(
    array("name" => "张三", "age" => 20, "score" => 80),
    array("name" => "李四", "age" => 21, "score" => 85),
    array("name" => "王五", "age" => 22, "score" => 90)
);

2. Why do you need to convert a two-dimensional array to a one-dimensional array?

During the development process, sometimes it is necessary to convert a two-dimensional array into a one-dimensional array. The following are some practical examples:

1. Database query result conversion

When using PHP to query the database, the query results are usually returned in the form of a two-dimensional array. If you want to perform statistics or sorting operations on query results, you may need to convert the two-dimensional array into a one-dimensional array. For example, when querying a student's average score, you need to convert the nested two-dimensional array into a one-dimensional array and then calculate the average score.

2. Processing JSON data

When using data in JSON format, it is sometimes necessary to convert nested two-dimensional arrays into one-dimensional arrays for ease of use.

3. Simplify array operations

For some simple array operations, using a one-dimensional array will be simpler, more efficient, and easier to understand. For example, using a one-dimensional array to store students' scores makes it easier to perform operations such as sorting, searching, and replacing.

3. How to convert a two-dimensional array into a one-dimensional array?

In PHP, there are many ways to convert a two-dimensional array to a one-dimensional array. The following are several implementation methods:

1. Use foreach loop implementation

You can use PHP’s foreach loop structure to traverse the two-dimensional array and insert each element into the one-dimensional array. middle. The following is a sample code:

$students = array(
    array("name" => "张三", "age" => 20, "score" => 80),
    array("name" => "李四", "age" => 21, "score" => 85),
    array("name" => "王五", "age" => 22, "score" => 90)
);

$flat_students = array(); // 定义一个空的一维数组

foreach ($students as $items) { // 遍历二维数组
    foreach ($items as $key => $value) { // 遍历内层数组
        $flat_students[$key][] = $value; // 将元素插入到一维数组中
    }
}

print_r($flat_students); // 输出一维数组

The output result is as follows:

Array
(
    [name] => Array
        (
            [0] => 张三
            [1] => 李四
            [2] => 王五
        )

    [age] => Array
        (
            [0] => 20
            [1] => 21
            [2] => 22
        )

    [score] => Array
        (
            [0] => 80
            [1] => 85
            [2] => 90
        )

)

2. Using the array_column() function to implement

PHP provides an array_column() function , you can extract the value corresponding to a key name in the two-dimensional array and return a one-dimensional array. The following is a sample code:

$students = array(
    array("name" => "张三", "age" => 20, "score" => 80),
    array("name" => "李四", "age" => 21, "score" => 85),
    array("name" => "王五", "age" => 22, "score" => 90)
);

$names = array_column($students, 'name');
$ages = array_column($students, 'age');
$scores = array_column($students, 'score');

print_r($names); // 输出一维数组
print_r($ages); // 输出一维数组
print_r($scores); // 输出一维数组

The output result is as follows:

Array
(
    [0] => 张三
    [1] => 李四
    [2] => 王五
)
Array
(
    [0] => 20
    [1] => 21
    [2] => 22
)
Array
(
    [0] => 80
    [1] => 85
    [2] => 90
)

3. Use the array_reduce() function to implement

The array_reduce() function in PHP can Iterates over the array elements and reduces them to a single value, then returns this value. You can convert a two-dimensional array into a one-dimensional array. The following is a sample code:

$students = array(
    array("name" => "张三", "age" => 20, "score" => 80),
    array("name" => "李四", "age" => 21, "score" => 85),
    array("name" => "王五", "age" => 22, "score" => 90)
);

$keys = array('name', 'age', 'score');

$flat_students = array_reduce($students, function ($result, $item) use ($keys) {
    foreach ($keys as $key) {
        $result[$key][] = $item[$key];
    }
    return $result;
}, array());

print_r($flat_students); // 输出一维数组

The output result is the same as the first method.

4. Summary

This article introduces several methods of converting two-dimensional arrays into one-dimensional arrays in PHP, including using foreach loop, array_column() function, array_reduce() function, etc. . Depending on actual needs, different methods can be chosen. Mastering these skills can allow us to process array data more efficiently and improve coding efficiency.

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