Array functions in PHP8: Detailed application skills of array_map()

In recent years, with the rapid development of the Internet industry, programming languages ​​​​are also constantly updated. As a more popular programming language, PHP is also developing under this trend. As the latest version, PHP8 has updated its built-in function library to provide more practical functions. This article will introduce the detailed application skills of the array function array_map() in PHP8.

1. Definition of array_map() function

array_map() function is a built-in function of PHP. Its definition is as follows:

array_map(callable $callback, array ... $arrays): array

Among them, the $callback parameter is the callback function, which is specifically defined as follows:

callable $callback(mixed ...$args): mixed

array_map The () function will operate the corresponding elements in each array by calling the callback function and return the new array result.

2. How to use the array_map() function

1. Operation on a single array

The first method is to operate on a single array. For example, we have an array $a whose elements are [1,2,3], and now we want to perform a square operation on each element, we can use the following code:

$a = [1 , 2, 3];
function square($n)
{

return $n ** 2;

}
$result = array_map('square', $a);
print_r($result );

The output result is [1, 4, 9].

2. Operation on multiple arrays

The second method is to operate on multiple arrays. Examples are as follows:

$a = [1, 2, 3];
$b = [4, 5, 6];
function add($x, $y)
{

return $x + $y;

}
$result = array_map('add', $a, $b);
print_r($result);

The output result is [5, 7, 9].

3. Anonymous function

PHP8 supports the use of anonymous functions, therefore, we can use anonymous functions to simplify the code. For example, the above example can be rewritten with the following code:

$a = [1, 2, 3];
$b = [4, 5, 6];
$result = array_map( function($x, $y){ return $x $y;}, $a, $b);
print_r($result);

The output result is [5, 7, 9].

4. Processing multi-dimensional arrays

We can also use the array_map() function to process multi-dimensional arrays. For example, we have an array $my_array whose elements are [[1,2], [3,4], [5,6]]. If we want to multiply each element, we can use the following code:

$my_array = [[1, 2], [3, 4], [5, 6]];
$result = array_map(function ($arr) {

return $arr[0] * $arr[1];

}, $my_array);
print_r($result);

The output result is [2, 12, 30].

5. Processing key and value

We can also use the array_map() function to process key and value at the same time. For example, we have an associative array $my_array whose elements are ['apple'=>1, 'banana'=>2, 'orange'=>3]. We want to operate on each element. This You can use the following code:

$my_array = ['apple'=>1, 'banana'=>2, 'orange'=>3];
$result = array_map(function ($k, $v) {

return $k . ':' . $v;

}, array_keys($my_array), $my_array);
print_r($result);

The output result is ['apple:1 ', 'banana:2', 'orange:3'].

3. Notes on the array_map() function

1. The number of array parameters must be the same

When using the array_map() function, pass in the array parameters The number must be the same, otherwise the error "Warning: array_map(): Argument #N is not an array" will occur.

2. The number of parameters of the callback function must also be the same

The number of parameters of the callback function should be the same as the number of arrays passed in, otherwise an error will occur in the program.

4. Summary

The array_map() function is one of the very practical array functions in PHP8. By combining the use of callback functions, you can quickly and conveniently operate on the elements in the array. This article introduces the following application skills of the array_map() function:

1. Operation on a single array
2. Operation on multiple arrays
3. Anonymous function
4. Processing multi-dimensional arrays
5. Processing key and value

The last thing to note is that when using the array_map() function, the number of incoming array parameters must be the same, and the parameters of the callback function The number must also be the same as the number of arrays passed in.

The above is the detailed content of Array functions in PHP8: Detailed application skills of array_map(). For more information, please follow other related articles on the PHP Chinese website!