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

Introduction

When working with PHP arrays, the array_rand function is a useful tool for selecting random keys. However, in some cases, you might need to recreate its functionality manually, such as when you’re avoiding built-in functions for learning purposes or coding challenges. In this guide, we’ll demonstrate how to replicate the behavior of array_rand without using any PHP array functions.

Why Avoid array_rand?

There are a few scenarios where you might want to avoid using array_rand:

• To better understand array manipulation.
• To improve coding skills by solving challenges.
• To meet specific requirements where built-in functions are restricted.

Manual Implementation of array_rand

Here’s a step-by-step guide to replicating the array_rand functionality.

Code Example:

function customArrayRand($array, $num = 1) {
    // Ensure input is an array
    if (!is_array($array)) {
        return null;
    }

    // Get the keys manually
    $keys = [];
    foreach ($array as $key => $value) {
        $keys[] = $key;
    }

    // Shuffle the keys
    for ($i = 0; $i < count($keys); $i++) {
        $randomIndex = rand(0, count($keys) - 1);
        $temp = $keys[$i];
        $keys[$i] = $keys[$randomIndex];
        $keys[$randomIndex] = $temp;
    }

    // Select the required number of keys
    $selectedKeys = [];
    for ($i = 0; $i < $num && $i < count($keys); $i++) {
        $selectedKeys[] = $keys[$i];
    }

    // Return a single key or an array of keys
    return $num === 1 ? $selectedKeys[0] : $selectedKeys;
}

// Example usage
$myArray = ["apple" => 1, "banana" => 2, "cherry" => 3];
$randomKey = customArrayRand($myArray);
print_r($randomKey);

$randomKeys = customArrayRand($myArray, 2);
print_r($randomKeys);

Output:

Explanation of the Code

1. Key Extraction: Instead of using array_keys, the function loops through the array and stores the keys manually.
2. Key Shuffling: A simple shuffle is performed using the Fisher-Yates algorithm approach.
3. Random Selection: Based on the $num parameter, one or more keys are selected.