1 2 3
8 9 4
7 6 5

7 8

1 2 3 4 5 6 7 8
26 27 28 29 30 31 32 9
25 44 45 46 47 48 33 10
24 43 54 57 56 49 34 11
23 42 53 52 51 50 35 12
22 41 40 39 38 37 36 13
21 20 19 18 17 16 15 14

function snake($row = 5, $col = 5)
{
  // 结果集
  $res = array();
  // 初始值
  $start = 1;
  // 当前遍历层数
  $flag = intval(($row + 1) / 2);
  for ($i = 1; $i <= $flag; $i++) {
    $startX = $i - 1;
    $startY = $i - 1;
    $width = $col - $i + 1;
    $height = $row - $i + 1;
    // 上
    for ($u = $startY; $u < $width; $u++) {
      $res[$startX][$u] = $start;
      $start += 1;
    }
    // 右
    for ($r = $startX + 1; $r < $height; $r++) {
      $res[$r][$u-1] = $start;
      $start += 1;
    }
    // 下
    for ($d = $u - 1 - 1; $d >= $startY; $d--) {
      $res[$r-1][$d] = $start;
      $start += 1;
    }
    // 左
    for ($l = $r - 1 - 1; $l >= $startX + 1; $l--) {
      $res[$l][$d+1] = $start;
      $start += 1;
    }
  }
  // 输出
  for ($i = 0; $i < $row; $i++) {
    for ($j = 0; $j < $col; $j++) {
      echo $res[$i][$j] . " ";
    }
    echo "<br />";
  }
}
snake(7, 8);

/* *
 * @param $w : 宽
 * @param $h : 高
 * @param $s : 起始数字
 * @param $x, $y : 起始位置坐标 只能从四顶点开始
 * @param $r :方向 默认顺时间 false为逆时针
 *
 */
function print_matrix($w, $h, $s = 1, $l = 1, $x = 0, $y = 0, $r = true) {
  // 表示四个方向
  $R = array(array(1, 0), array(0, 1), array(-1, 0), array(0, -1));
  !$r && $R = array_reverse($R);
  // 创建一个无限迭代器
  $iterator = new InfiniteIterator(new ArrayIterator($R));
  $iterator->rewind();
  list($_x, $_y) = $iterator->current();
  $result = [];
  $result[$x][$y] = $s;
  for ($i = $s+1; $i < ($s + $w * $h); $i++) {
    $new_x = $x + $_x;
    $new_y = $y + $_y;
    if (0 <= $new_x && 0 <= $new_y && $new_x < $w && $new_y < $h && !isset($result[$new_x][$new_y])) {
      $result[$new_x][$new_y] = $i;
      $x = $new_x;
      $y = $new_y;
    } else {
      $iterator->next();
      list($_x, $_y) = $iterator->current();
      $i--;
    }
  }
  // 打印
  for ($i = 0; $i < $h; $i++) {
    for ($j = 0; $j < $w; $j++) {
      echo $result[$j][$i], "\t";
    }
    echo "<br />";
  }
}