Array functions in PHP8: efficient data processing method of array_map()

The newly added array function in PHP8-array_map() is an efficient data processing method. It can process the elements in the array one by one without modifying the original array, and the processing results form a new array. This article will introduce the usage of array_map() function and its application in data processing.

1. Basic usage of array_map() function

The syntax of array_map() function is as follows:

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

The first parameter of this function, $callback, is a callable function or method, and the second parameter is one or more arrays. The array_map() function will take out the elements at the same subscript position according to the array specified in the parameter, pass it into the callback function for processing, and return the processing results into a new array. Therefore, the array parameters passed in must be of the same length.

The following is a simple example that shows using the array_map() function to square the elements in an array and return a new array:

$array = [1, 2, 3, 4, 5];
function square($x) {
    return $x * $x;
}
$result = array_map('square', $array);
print_r($result);
// 输出：[1, 4, 9, 16, 25]

In the above example, we define a function square (), this function can calculate the square of a number. We pass the function name as a parameter to the array_map() function, pass the array to be processed as the second parameter, and receive the new array returned.

2. Advanced usage of array_map() function

In addition to basic usage, array_map() function also has some advanced usage, which can be easily applied in data processing.

1. Processing multiple arrays

The array_map() function can process multiple arrays, combine elements at the same subscript position in different arrays and pass them into the callback function . The following is an example of using the array_map() function to process two arrays:

$array1 = [1, 2, 3];
$array2 = [4, 5, 6];
function combine($x, $y) {
    return $x * $y;
}
$result = array_map('combine', $array1, $array2);
print_r($result);
// 输出：[4, 10, 18]

In the above example, we defined a callback function combine(), which combines elements with the same subscript position in the two arrays. Performs a multiplication calculation and returns the result. We pass the function name as a parameter into the array_map() function, pass in the two arrays to be processed as parameters, and receive the returned new array.

2. Processing multi-dimensional arrays

The array_map() function can also process multi-dimensional arrays, and for two-dimensional arrays or higher-dimensional arrays, you can specify the processing dimensions. The following is an example of using the array_map() function to process a two-dimensional array:

$array = [
    [1, 2, 3],
    [4, 5, 6]
];
function sum($arr) {
    return array_sum($arr);
}
$result = array_map('sum', $array);
print_r($result);
// 输出：[6, 15]

In the above example, we define a callback function sum(), which calculates the sum of the elements of the array and returns the calculation result. We pass the function name as a parameter to the array_map() function, pass the array to be processed as a parameter, and receive the returned new array.

When processing multi-dimensional arrays, we can specify the dimension parameter to indicate which dimension of elements to process. The following is an example of using the array_map() function to process a three-dimensional array:

$array = [
    [
        [1, 2],
        [3, 4]
    ],
    [
        [5, 6],
        [7, 8]
    ]
];
function sum($arr) {
    return array_sum($arr);
}
$result = array_map('sum', array_column($array, 0), array_column($array, 1));
print_r($result);
// 输出：[16, 20]

In the above example, we convert the three-dimensional array to be processed into two two-dimensional arrays, one of which is the first dimension. The elements of another two-dimensional array are the elements of the second dimension. We pass these two arrays as parameters into the array_map() function at the same time, and specify the callback function sum(), and finally get a new one-dimensional array.

3. Performance optimization of array_map() function

When using array_map() function, we need to pay attention to the performance optimization issues. If the array that needs to be processed is large and the callback function for processing is very simple, you can consider using a foreach() loop for data processing to improve operating efficiency.

The following is a performance comparison of using the array_map() function to process large-scale arrays:

$array = range(1, 100000);
$start_time = microtime(true);
function add1($n) {
    return $n + 1;
}
$result = array_map('add1', $array);
$end_time = microtime(true);
echo 'array_map()函数耗时：' . ($end_time - $start_time) . '秒';

$start_time = microtime(true);
foreach ($array as &$n) {
    $n += 1;
}
$result = $array;
$end_time = microtime(true);
echo 'foreach()函数耗时：' . ($end_time - $start_time) . '秒';

In the above example, we use the array_map() function and the foreach() loop to process an array containing 10 For an array of ten thousand elements, both methods add 1 to each element in the array and return a new array. As can be seen from the running results, using foreach() for data processing is faster than using the array_map() function.

4. Summary

array_map() function is a newly added efficient data processing method in PHP8. It can process the elements in the array without modifying the original array, and Returns a new array composed of processing results. In addition to basic usage, the array_map() function also has some advanced usage that can be applied in data processing. However, when using the array_map() function for data processing, we need to pay attention to the performance optimization issues to improve the running efficiency of the code.

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