PHP设计模式之迭代器（Iterator）模式入门与应用详(3)

class Fibonacci implements Iterator {
  private $previous = 1;
  private $current = 0;
  private $key = 0;
   
  public function current() {
    return $this->current;
  }
   
  public function key() {
    return $this->key;
  }
   
  public function next() {
    // 关键在这里
    // 将当前值保存到 $newprevious
    $newprevious = $this->current;
    // 将上一个值与当前值的和赋给当前值
    $this->current += $this->previous;
    // 前一个当前值赋给上一个值
    $this->previous = $newprevious;
    $this->key++;
  }
   
  public function rewind() {
    $this->previous = 1;
    $this->current = 0;
    $this->key = 0;
  }
   
  public function valid() {
    return true;
  }
}
 
$seq = new Fibonacci;
$i = 0;
foreach ($seq as $f) {
  echo "$f ";
  if ($i++ === 15) break;
}