Introduction to PHP functions: array_column() function

PHP function introduction: array_column() function

Introduction:
In PHP programming, we often need to extract the value of a specific key from a multi-dimensional array. This You can use the array_column() function. This article will introduce the usage and code examples of the array_column() function in detail.

The array_column() function is a function only available in PHP version 5.5.0 and above. It can extract the value of the specified key from a multi-dimensional array and return a one-dimensional array containing the specified key value.

Syntax:
array_column(array $input, mixed $column_key [, mixed $index_key = null])

Parameter description:
$input: required. Multidimensional Arrays.
$column_key: required. The key name to extract.
$index_key: optional. Used as an index/key into the returned array.

Return value:
Returns a one-dimensional array containing the specified key value.

Code example:
The following is a simple example that demonstrates how to use the array_column() function to extract the value of a specified key from a multidimensional array:

<?php
$users = [
    ['id' => 1, 'name' => 'John', 'email' => 'john@example.com'],
    ['id' => 2, 'name' => 'Jane', 'email' => 'jane@example.com'],
    ['id' => 3, 'name' => 'Smith', 'email' => 'smith@example.com'],
];

// 从多维数组中提取'name'键的值
$names = array_column($users, 'name');
print_r($names);

// 结果：Array ( [0] => John [1] => Jane [2] => Smith )
?>

The above code creates a user Multidimensional array of messages $users. Then, the value corresponding to the 'name' key in the array is extracted through the array_column() function and assigned to the $names variable, and finally the $names array is printed.

Result:
Array ( [0] => John [1] => Jane [2] => Smith )

Further expansion:
array_column() The function can also use a key as the index or key of the returned array by specifying the $index_key parameter. The following is a sample code:

<?php
$users = [
    [
        'id' => 1,
        'name' => 'John',
        'email' => 'john@example.com',
        'age' => 25
    ],
    [
        'id' => 2,
        'name' => 'Jane',
        'email' => 'jane@example.com',
        'age' => 30
    ],
    [
        'id' => 3,
        'name' => 'Smith',
        'email' => 'smith@example.com',
        'age' => 35
    ],
];

// 提取'id'键作为索引，'name'键作为值的关联数组
$result = array_column($users, 'name', 'id');
print_r($result);

// 结果：Array ( [1] => John [2] => Jane [3] => Smith )
?>

In the above code, we generate an associative array by specifying the $index_key parameter to use the 'id' key as the index and the 'name' key as the value.

Summary:
The array_column() function is a very practical and convenient function, which can simplify our operation of extracting specific key values ​​​​in multi-dimensional arrays in PHP programming. Through the introduction and code examples of this article, I believe you will have a deeper understanding and mastery of the array_column() function.

Reference:

• PHP Manual: https://www.php.net/manual/en/function.array-column.php

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