PHP converts multi-dimensional array into one-dimensional array

PHP is a very flexible and versatile programming language. Among them, multidimensional array is one of the most common data structures in programming. However, on some occasions, we need to flatten multi-dimensional arrays into one-dimensional arrays for unified processing. In this article, we will introduce in detail how to convert a multi-dimensional array into a one-dimensional array.

1. Use the array_walk_recursive() function to flatten multi-dimensional arrays

In PHP, the array_walk_recursive() function can traverse each element in a multi-dimensional array and then convert it into One-dimensional array. The following is a sample code that uses the array_walk_recursive() function to convert a multi-dimensional array into a one-dimensional array:

function array_flatten($array) {
    $flatten = [];
    array_walk_recursive($array, function($value) use(&$flatten) {
        $flatten[] = $value;
    });
    return $flatten;
}

The sample code uses a closure function to traverse a multi-dimensional array. The array_walk_recursive() function traverses a multi-dimensional array, adds each element to a new one-dimensional array, and finally returns the new array.

2. Use the array_reduce() function to flatten multi-dimensional arrays

In addition to the array_walk_recursive() function, PHP's array_reduce() function can also flatten multi-dimensional arrays. The following is a sample code that uses the array_reduce() function to convert a multi-dimensional array into a one-dimensional array:

function array_flatten($array) {
    return array_reduce($array, function($result, $item) {
        if (is_array($item)) {
            $result = array_merge($result, array_flatten($item));
        } else {
            $result[] = $item;
        }
        return $result;
    }, []);
}

The sample code uses a recursive function to traverse a multi-dimensional array. By judging whether the element is an array, each element in the array is traversed and merged, and finally the multi-dimensional array is converted into a one-dimensional array.

3. Use foreach loop to flatten multi-dimensional arrays

If you are not familiar with recursion and functional programming, you can use foreach loop to flatten multi-dimensional arrays. The following is a sample code that uses a foreach loop to convert a multi-dimensional array into a one-dimensional array:

function array_flatten($array) {
    $flatten = [];
    foreach ($array as $value) {
        if (is_array($value)) {
            $flatten = array_merge($flatten, array_flatten($value));
        } else {
            $flatten[] = $value;
        }
    }
    return $flatten;
}

The sample code uses a foreach loop to traverse the multi-dimensional array, and then performs further traversal and conversion through recursion. When traversing to an element that is an array, continue traversing and processing the element; when traversing to an element that is not an array, add the element to a new one-dimensional array.

Summary

There are many ways to convert a multi-dimensional array into a one-dimensional array in PHP, including using the array_walk_recursive() function, array_reduce() function, and using recursion and foreach loops wait. Which method to choose should be determined according to the actual situation and used flexibly to achieve the best effect and code clarity.

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