用PHP迭代器来实现一个斐波纳契数列

<?php

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;

}