Comprehensive Guide to PHP Array Union: Efficiently Merge Multiple Arrays

What Is an Array Union

In computer science, a set is a data structure used to store unique elements. Similarly, PHP arrays can perform set-related operations such as intersection, union, and difference. This article focuses on how to perform array union operations in PHP.

Array Union Operations in PHP

Using a Custom Function to Implement Array Union

PHP's built-in array_intersect() function retrieves the intersection of arrays. To get the union of multiple arrays, you can merge all arrays first and then remove duplicates. Here's an example:

function array_union(...$arrays) {
    $result = [];
    foreach ($arrays as $array) {
        $result = array_merge($result, $array);
    }
    $result = array_unique($result);
    return $result;
}

This function merges all input arrays and then removes duplicate values using array_unique(), producing the union of the arrays.

Simplifying with array_merge

You can also achieve the union more concisely by combining PHP's variable-length arguments with array_merge() and array_unique():

function array_union(...$arrays) {
    return array_unique(array_merge(...$arrays));
}

This approach also merges multiple arrays and removes duplicates with simple and readable code.

Example Code

Here is an example demonstrating how to use the function to get the union of arrays:

$array1 = [1, 2, 3];
$array2 = [2, 3, 4];
$array3 = [3, 4, 5];
$result = array_union($array1, $array2, $array3);
print_r($result);

The output will be:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
)

Conclusion

This article demonstrated that PHP's array union can be easily implemented by merging arrays and removing duplicates. Whether using a custom function or PHP's built-in array_merge() and array_unique(), you can efficiently combine multiple arrays. Understanding and applying these functions effectively makes array operations simpler and more efficient.