php选择排序是什么意思

<?php

function selectionSort ($arr) {

        $count = count($arr);

        for ($i = 0; $i < $count - 1; $i++) {

                $minIndex = $i;

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

                        if ($arr[$minIndex] > $arr[$j]) {

                                $minIndex = $j;

                        }

                }

                if ($minIndex != $i) {

                        $temp = $arr[$i];

                        $arr[$i] = $arr[$minIndex];

                        $arr[$minIndex] = $temp;

                }

        }

        return $arr;

}

$arr = [15, 3, 6, 43, 132, 4, 28, 39, 99];

$res = selectionSort($arr);

print_r($res);