Welcome! Today, we will explore an interesting task using PHP arrays: pairing up 'opposite' elements. This lesson aims to improve your array-handling skills within PHP. Arrays are a fundamental tool in PHP, providing an efficient way to store and manipulate collections of data. Are you ready to get started? Let's dive into the world of PHP arrays!

Our task today is to form pairs of 'opposite' elements in a given PHP array of integers. In an array consisting of n elements, the first and last elements are considered 'opposite', the second element and the second-last element are 'opposite', and so on. For an array with an odd length, the middle element is its own 'opposite'.

You will receive an array of n integers. The value of n could range from 1 to 100, inclusive. The task requires you to return an array of strings, where each string consists of an element paired with its 'opposite' element, joined by a space.

For instance, consider an array $numbers as [1, 2, 3, 4, 5]. In this case, the output should be ["1 5", "2 4", "3 3", "4 2", "5 1"].

Let's start by understanding how to access elements in a PHP array.

In PHP, the i-th element of an array $numbers can be accessed using $numbers[$i], where the index starts from 0. Consequently, the first element is $numbers[0], the second is $numbers[1], and so on, up to $numbers[count($numbers) - 1] for the last element.

Here's how you can access an element in a PHP array:

php
Copy to clipboard
1$numbers = [1, 2, 3, 4, 5];
2$i = 0;
3$elementAtGivenIndex = $numbers[$i];

Now, let's figure out how to access an element's 'opposite'.

The 'opposite' of the i-th element in the array is located at the count($numbers) - $i - 1 index. Continuing with our analogy, imagine standing at one end of a line while your friend is on the opposite end. You and your friend can be viewed as 'opposites'. Similarly, the 'opposite' of $numbers[0] is $numbers[count($numbers) - 0 - 1], and the 'opposite' of $numbers[1] is $numbers[count($numbers) - 1 - 1], and so on.

Understanding how to locate an element's 'opposite' allows us to proceed with coding our solution. Let's initialize an empty array named $result to store our 'opposite' pairs and compute the size of the array for future reference.

php
Copy to clipboard
1$numbers = [1, 2, 3, 4, 5];
2$result = [];
3$n = count($numbers);

The next step involves looping through all elements in our $numbers array. In this loop, we will create a string for each pairing of 'opposite' elements. This string contains the i-th element and the n - i - 1-th element, separated by a space. Each pair will then be added to our $result array. Here's the complete PHP function:

php
Copy to clipboard
1<?php
2
3function solution($numbers) {
4    $result = [];
5    $n = count($numbers);
6    for ($i = 0; $i < $n; $i++) {
7        $result[] = $numbers[$i] . " " . $numbers[$n - $i - 1];
8    }
9    return $result;
10}
11
12$numbers = [1, 2, 3, 4, 5];
13print_r(solution($numbers));

This function iterates through the $numbers array, forming a string with each element's 'opposite' and adding the pair to the $result array.

Congratulations! You've successfully explored the concept of 'opposite' element pairs and array indexing in PHP. By now, you should be acquainted with accessing and pairing elements in a PHP array based on their positions. This foundational skill moves you closer to mastering array manipulation in PHP. Up next, we have prepared several exercises for you to apply and further practice what you've learned. Remember, practice is the key to mastering these concepts. Keep up the great work, and happy coding!