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 $value . "\n";
}
PHP生成器
生成器使用yield关键字返回结果，和python一样。yield会直接生产一个结果，下次调用时会从上次yield处继续执行。
function Fb($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";
}
