What Does array_walk Do?

The array_walk function applies a user-defined callback function to each element in an array. It can also pass the array key as a parameter to the callback.

The array_walk function in PHP is a powerful tool that allows you to apply a custom callback function to each element of an array. But what if you’re unable to use built-in array functions or want to explore how it works internally? This post  will show you how to manually implement the behavior of array_walk.

Example:

$input = ['a' => 'apple', 'b' => 'banana', 'c' => 'cherry'];

array_walk($input, function (&$value, $key) {
    $value = strtoupper($value);
});

// Output: ['a' => 'APPLE', 'b' => 'BANANA', 'c' => 'CHERRY']

Manual Implementation of array_walk in PHP

Here’s how you can replicate this functionality without using the array_walk function.

Example:

function manualArrayWalk(&$array, $callback) {
    foreach ($array as $key => &$value) {
        $callback($value, $key);
    }
}

// Test Case
$input = ['a' => 'apple', 'b' => 'banana', 'c' => 'cherry'];

manualArrayWalk($input, function (&$value, $key) {
    $value = strtoupper($value);
});

// Output
print_r($input);

Output:

Array
(
    [a] => APPLE
    [b] => BANANA
    [c] => CHERRY
)

How It Works:

1. Define the Function:
   Create a function named manualArrayWalk that accepts two parameters:
   • The array (passed by reference).
   • A callback function.
2. Loop Through the Array:
   Use a foreach loop to iterate over the array, passing both the key and value.
3. Apply the Callback:
   Call the callback function for each element, passing the value and key as arguments. The value is passed by reference, allowing modifications.
4. Test the Function:
   Provide an array and a callback function to test its functionality.

Why Avoid Built-in Functions?

• Understanding Core Concepts: By building it yourself, you gain a deeper understanding of PHP’s array handling.
• Customizable Logic: You can tweak the function to suit your specific needs.

Keep Learning 🙂