Which PHP Array Manipulation Function is Right For You: array_map, array_walk, or array_filter?

Distinguishing Array Manipulation Functions: array_map, array_walk, and array_filter

Array_map, array_walk, and array_filter are three PHP functions commonly used to iterate over and manipulate arrays. While they share the functionality of applying a callback function to an array, they differ in certain key aspects.

Modifying Array Values

Array_walk allows for modifying the values of the input array during iteration, while array_map does not. This distinction is crucial if you intend to modify array elements in-place.

Array Key Access

Array_map operates solely on the values of an array, ignoring its keys. In contrast, array_walk provides access to both array keys and values, allowing for key-based manipulations.

Return Value

Array_map returns a new array transformed by the callback function, while array_walk returns a boolean value indicating the success of its operation. If you require a new array as the result, array_map is the appropriate choice. Otherwise, array_walk can yield better performance.

Iterating Multiple Arrays

Array_map can handle multiple input arrays, simultaneously iterating over them and applying the callback function in parallel. Array_walk, on the other hand, operates on a single array at a time.

Callback Parameter

Array_walk supports the passing of an additional parameter to the callback function. This parameter can be useful for providing additional context or data to the callback logic. However, due to the introduction of anonymous functions in PHP 5.3, this feature is generally less relevant.

Size of Returned Array

The length of the returned array in array_map matches the length of the longest input array. Array_walk does not return an array, and its operation does not affect the original array's size. Array_filter, on the other hand, retains the subset of elements that meet the callback condition.

Example

To illustrate these differences, consider the following example:

<code class="php">$origArray1 = [2.4, 2.6, 3.5];
$origArray2 = [2.4, 2.6, 3.5];

// array_map: cannot modify values
$result1 = array_map('floor', $origArray1);
print_r($result1); // Does not change $origArray1

// array_walk: can modify values
array_walk($origArray2, function (&$value, $key) { $value = floor($value); });
print_r($origArray2); // Modifies $origArray2

// array_filter: select elements
$result2 = array_filter($origArray1, function($value) { return $value > 2.5; });
print_r($result2); // Only returns elements greater than 2.5</code>

This example demonstrates how each function differs and highlights their suitability for specific scenarios. Understanding these distinctions will help you select the most appropriate function for your array manipulation needs.

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