PHP四种排序算法(选择排序)

$arr = [3,2,5,1,7,6];
function select($arr) {
    $len = count($arr);
    if ($len <= 1) {
        return $arr;
    }
    for ($i = 0; $i<$len-1; $i++) {
        $p = $i;
        for ($j = $i+1; $j<$len;$j++){
            if ($arr[$p]>$arr[$j]) {
                $p = $j;
            }
        }
        if ($p!=$i) {
            $tmp = $arr[$p];
            $arr[$p] = $arr[$i];
            $arr[$i] = $tmp;
        }
    }
    return $arr;
}
var_dump(select($arr));
die;