How to Implement PHP’s array_replace_recursive Without Using Built-In Functions

Introduction

The array_replace_recursive function in PHP is used to replace values in a multi-dimensional array recursively, with values from one or more arrays. But what if you need to achieve this without using the built-in function? This guide provides a step-by-step approach to implement array_replace_recursive manually using basic PHP constructs.

Why Avoid array_replace_recursive?

Avoiding built-in functions can be useful for:

• Gaining a deeper understanding of recursion and arrays.
• Tackling coding challenges where built-in functions are restricted.
• Customizing the functionality to meet unique requirements.

Manual Implementation of array_replace_recursive

Code Example

Here’s a custom implementation of array_replace_recursive:

function customArrayReplaceRecursive($array1, ...$arrays) {
    // Ensure the first parameter is an array
    if (!is_array($array1)) {
        return [];
    }

    // Start with the base array
    $result = $array1;

    // Iterate through the additional arrays
    foreach ($arrays as $array) {
        if (is_array($array)) {
            foreach ($array as $key => $value) {
                // Check if the value is an array and the key exists in the base array
                if (is_array($value) && isset($result[$key]) && is_array($result[$key])) {
                    // Recursive call for nested arrays
                    $result[$key] = customArrayReplaceRecursive($result[$key], $value);
                } else {
                    // Replace or add the value from the current array
                    $result[$key] = $value;
                }
            }
        }
    }

    return $result;
}

// Example usage
$array1 = [
    "a" => ["x" => "apple", "y" => "banana"],
    "b" => "cherry",
    "c" => ["z" => "dragonfruit"]
];
$array2 = [
    "a" => ["y" => "blueberry"],
    "c" => ["z" => "elderberry", "w" => "fig"],
    "d" => "grape"
];

$result = customArrayReplaceRecursive($array1, $array2);

print_r($result);

Output:

Array
(
    [a] => Array
        (
            [x] => apple
            [y] => blueberry
        )

    [b] => cherry
    [c] => Array
        (
            [z] => elderberry
            [w] => fig
        )

    [d] => grape
)

Explanation of the Code

1. Input Validation: The function ensures the first argument is an array.
2. Base Array Initialization: The $result starts as a copy of $array1.
3. Recursive Replacement: If a value is an array and the corresponding key exists in $result, the function calls itself to handle nested arrays.
4. Replace/Add Values: Non-array values are replaced or added directly.
5. Final Output: The modified array, with replacements applied recursively, is returned.