PHP如何实现选择排序？

<?php

function selection_sort($data)
{
    for($i=0; $i<count($data)-1; $i++) {
        $min = $i;
        for($j=$i+1; $j<count($data); $j++) {
            if ($data[$j]<$data[$min]) {
                $min = $j;
            }
        }
        $data = swap_positions($data, $i, $min);
    }
    return $data;
}

function swap_positions($data1, $left, $right) {
    $backup_old_data_right_value = $data1[$right];
    $data1[$right] = $data1[$left];
    $data1[$left] = $backup_old_data_right_value;
    return $data1;
}
$my_array = array(3, 0, 2, 5, -1, 4, 1);
echo "原始数组:\n";
echo implode(', ',$my_array );
echo "\n排序后数组:\n";
echo implode(', ',selection_sort($my_array)). PHP_EOL;

原始数组: 3, 0, 2, 5, -1, 4, 1 
排序后数组: -1, 0, 1, 2, 3, 4, 5