Sorting Brilliance: Insertion Sort in PHP

Sorting Brilliance: Insertion Sort in PHP

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Sorting is a crucial operation in computer science, and understanding different sorting algorithms is essential for efficient problem-solving. In this blog post, we will explore the concept of insertion sort and walk through its implementation using PHP. By the end, you'll have a clear understanding of this sorting technique and how to implement it effectively.

Understanding Insertion Sort:

Insertion sort is a simple comparison-based sorting algorithm that builds the final sorted array one element at a time. It works by dividing the input array into two parts: the sorted part at the left end and the unsorted part at the right end. The algorithm iterates through the unsorted part, selects an element, and places it in the correct position within the sorted part by shifting larger elements to the right. This process continues until the entire array is sorted. Insertion sort has a time complexity of O(n^2) but performs well for small arrays or partially sorted arrays.

Implementing Insertion Sort in PHP:

Let's delve into the implementation of the insertion sort algorithm using PHP. We'll define a function called insertionSort that takes in an array to sort.

function insertionSort($array) {
    $length = count($array);

    for ($i = 1; $i < $length; $i++) {
        $key = $array[$i];
        $j = $i - 1;

        while ($j >= 0 && $array[$j] > $key) {
            $array[$j + 1] = $array[$j];

        $array[$j + 1] = $key;

    return $array;

Explanation of the Implementation:

  1. The insertionSort function takes an array as input and returns the sorted array.

  2. We determine the length of the array using the count function and store it in the $length variable.

  3. We start iterating from the second element (index 1) since the first element is considered already sorted.

  4. Inside the loop, we store the current element $key and initialize a variable $j to the index before the current element.

  5. We compare the current element with the elements in the sorted part of the array, moving them to the right if they are greater than the current element.

  6. We continue this process until we find the correct position for the current element or reach the beginning of the array.

  7. Finally, we insert the current element $key into its correct position in the sorted part of the array.

  8. This process repeats until the entire array is sorted.

  9. Finally, we return the sorted array.

Example Usage: Now, let's see the insertion sort algorithm in action with an example:

$data = [9, 3, 7, 1, 5];
$sortedArray = insertionSort($data);

echo "Sorted Array: ";
foreach ($sortedArray as $element) {
    echo $element . " ";

In this example, we have an array called $data containing integer values. We want to sort this array using the insertionSort function. The sorted array is then displayed using a foreach loop.


Insertion sort, with its intuitive logic and straightforward implementation, serves as a valuable sorting algorithm. In this blog post, we explored the concept of insertion sort and implemented it using PHP. While insertion sort may not be the most efficient algorithm for large datasets, understanding its mechanics contributes to a solid foundation in sorting techniques. So go ahead, leverage insertion sort when appropriate, and embrace the brilliance of sorting!