Welcome to another pivotal lesson in your interview preparation. In this lesson, we will concentrate on Advanced Array Manipulation Techniques, focusing on the representation and manipulation of arrays directly, without relying on built-in functions. This topic is indispensable when preparing for technical interviews, as many problems often involve performing various operations on arrays.

Take, for example, the PHP code provided for rotating an array by k positions. The operation can appear complex initially, but it becomes simple by understanding how array indices function. In PHP, arrays are flexible in size, and we can use loops or manual approaches to achieve the desired operations.

In this example, we will manually perform a rotation by k positions using a series of steps to break down and reassemble the array content.

Here's how the code looks in PHP:

php
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1<?php
2
3class Solution {
4
5    public static function rotateArray(&$nums, $k) {
6        // Ensure k is within the bounds of the array length
7        $k = $k % count($nums);
8        // Reverse the entire array
9        self::reverse($nums, 0, count($nums) - 1);
10        // Reverse the first k elements
11        self::reverse($nums, 0, $k - 1);
12        // Reverse the rest of the array
13        self::reverse($nums, $k, count($nums) - 1);
14    }
15
16    private static function reverse(&$nums, $start, $end) {
17        while ($start < $end) {
18            $temp = $nums[$start];
19            $nums[$start] = $nums[$end];
20            $nums[$end] = $temp;
21            $start++;
22            $end--;
23        }
24    }
25
26    public static function main() {
27        $nums = array(1, 2, 3, 4, 5, 6, 7);
28        $k = 3;
29        self::rotateArray($nums, $k);
30        foreach ($nums as $num) {
31            echo $num . " ";
32        }
33        // Output: 5 6 7 1 2 3 4
34    }
35}
36
37?>

In this example, when k = 3, the algorithm first reverses the entire array, resulting in [7, 6, 5, 4, 3, 2, 1]. Then, it reverses the first k elements, giving us [5, 6, 7, 4, 3, 2, 1], and finally reverses the rest of the array to get [5, 6, 7, 1, 2, 3, 4], achieving the desired rotation.

Developing proficiency in Advanced Array Manipulation Techniques is rewarding and powerful, as it not only opens up efficient ways to solve problems that may appear convoluted at first, but also cultivates the skills necessary for handling even more complex algorithms. Through practice exercises, we aim to equip you with an intuitive understanding of these techniques, which will significantly aid you in your problem-solving abilities. So, let's get started!