array_replace_lists_recursive.php

<?php

/**
 * Recursively replaces list arrays and merges associative arrays within a given array.
 *
 * This function differs from `array_replace_recursive()` by only replacing list arrays
 * recursively, while associative arrays are merged. Conversely, it differs from
 * `array_merge_recursive()` by merging only associative arrays recursively, while list
 * arrays are replaced.
 *
 * This method ensures list arrays are completely refreshed with the new values,
 * and associative arrays are intelligently combined. This preserves structural integrity
 * and updates content only where necessary, making it suitable for complex data structures
 * where different merge behaviors are needed for lists and associative arrays.
 *
 * @link https://gist.github.com/fjarrett/070182402c85eacf383b64ba5098c3e4 Example usage
 */
function array_replace_lists_recursive(array $array, array ...$replacements): array
{
    foreach ($replacements as $replacement) {
        foreach ($replacement as $key => $value) {
            if (isset($array[$key]) && is_array($value) && is_array($array[$key])) {
                $array[$key] = array_is_list($value) ? $value : array_replace_lists_recursive($array[$key], $value);
            } else {
                $array[$key] = $value;
            }
        }
    }

    return $array;
}

$a = [
    'foo' => [
        'bar' => 'a',
        'baz' => [1, 2, 3],
        'qux' => 'c',
        'old' => 1,
    ],
];

$b = [
    'foo' => [
        'bar' => 'b',
        'baz' => [1, 3],
        'new' => 'd',
    ],
];

$c = [
    'foo' => [
        'qux' => 'updated c',
    ],
];

echo '<pre>' . var_export(array_replace_lists_recursive($a, $b, $c), true) . '</pre>';

// [
//     'foo' => [
//         'bar' => 'b',
//         'baz' => [1, 3],
//         'qux' => 'updated c',
//         'old' => 0,
//         'new' => 'd',
//     ],
// ];

ArrayReplaceListsRecursiveTests.php

<?php

namespace Tests;

use PHPUnit\Framework\TestCase;

class ArrayReplaceListsRecursiveTests extends TestCase
{
    public function test_array_replace_lists_recursive()
    {
        $array = [
            'foo' => [
                'bar' => 'a',
                'baz' => [1, 2, 3],
                'qux' => 'c',
                'old' => 1,
            ],
        ];

        $replacement1 = [
            'foo' => [
                'bar' => 'b',
                'baz' => [4, 5],
                'new' => 'd',
            ],
        ];

        $replacement2 = [
            'foo' => [
                'qux' => 'updated c',
            ],
        ];

        $expected = [
            'foo' => [
                'bar' => 'b',
                'baz' => [4, 5],
                'qux' => 'updated c',
                'old' => 1,
                'new' => 'd',
            ],
        ];

        $actual = array_replace_lists_recursive($array, $replacement1, $replacement2);

        $this->assertEquals($expected, $actual);
    }
}