When to Use array_map, array_walk, and array_filter in PHP?

Explaining the Differences between array_map, array_walk, and array_filter

Array functions in PHP provide convenient ways to manipulate arrays. Among these, array_map, array_walk, and array_filter are commonly used. While they share similarities, there are key distinctions in their behavior.

Functionality Overview

• array_map: Applies a callback function to each element of the array(s) and returns a new array containing the results.
• array_walk: Applies a callback function to each element of the array and updates the original array in place.
• array_filter: Removes elements from the array based on a callback function, returning a new array containing only the elements that pass the condition.

Key Differences

• Array Modification: array_walk modifies the original array, while array_map does not.
• Key Access: array_walk allows access to array keys within the callback function, while array_map does not.
• Return Values: array_map returns a new array, while array_walk returns true. array_filter also returns a new array, but only contains the filtered elements.
• Iteration: array_map can iterate over multiple arrays simultaneously, while array_walk only iterates over one array.
• Arbitrary Data Passing: array_walk can accept an additional parameter to pass to the callback, an option introduced in PHP 5.3.
• Returned Array Length: array_map's resulting array matches the length of the largest input array, while array_walk's array does not change length. array_filter returns an array that matches the length of the filtered elements.

Illustrative Examples

<code class="php">$a = [2.4, 2.6, 3.5];

// array_map
$b = array_map('floor', $a); // $a remains unchanged
print_r($b); // Output: [2, 2, 3]

// array_walk
array_walk($a, 'floor'); // Modifies $a
print_r($a); // Output: [2, 2, 3]

// array_filter
$c = array_filter($a, fn($v) => $v > 2.5); // Filter elements
print_r($c); // Output: [2.6, 3.5]</code>

In conclusion, array_map, array_walk, and array_filter each have specific roles in array manipulation. Understanding their differences allows developers to choose the most appropriate function for their task.

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