Selection Sort Algorithm in PHP

Even with similar complexity of O(n^2) as Bubble Sort, selection sort is preferred when memory writes are too expensive. If you want to understand how it works, jump to bottom of the page to see a quick video. Find below the algorithm.

function selectionSort($arr) : array
    $arrLength = count($arr);

    for($i = 0; $i < $arrLength; ++$i) {

        for($j = $i+1; $j < $arrLength; ++$j) {

            if($arr[$j] < $arr[$i]) {

                $min = $arr[$j];
                $arr[$j] = $arr[$i];
                $arr[$i] = $min;


    return $arr;

Source Code of Algorithm Series:

Understand Selection Sort: