斐波那契数列，使用PHP迭代器、生成器实现

斐波那契数列其数学定义为：F0=1，F1=1，Fn=F(n-1)+F(n-2)（n>=2）

普通解法for循环

<?php $arr[1] = 1; for($i = 2;$i < 100;$i++) { $arr[$i] = $arr[$i-1] + $arr[$i-2]; } echo join(",",$arr);//将数组合并为一个字符串输出 ?>

PHP 迭代器

PHP 迭代器 继承Iterator 接口，实现5个方法即可 而生成器循环返回的是中间值

class Fb implements Iterator { public function __construct($len) { $this->len = $len; } private $len = 0; private $pre = 1; private $curr = 1; private $count = 0; public function current() { return $this->curr; } public function next() { $tmp = $this->curr; $this->curr += $this->pre; $this->pre = $tmp; $this->count++; } public function key() { // return $this->key; } public function valid() { return $this->count < $this->len; } public function rewind() { $this->pre = 1; $this->curr = 1; } } foreach ((new Fb(40)) as $value) { echo $value . "\n"; }

PHP生成器

生成器使用yield关键字返回结果，和python一样。yield会直接返回结果，下次调用时会从上次yield处继续执行。

function Fb($len) { $pre = 1; $curr = 1; $count = 1; while ($count <= $len) { yield $curr; $tmp = $curr; $curr += $pre; $pre = $tmp; $count++; } } foreach (Fb(40) as $value) { echo $value . "\n"; }