Using a PHP iterator to implement a Fibonacci sequence

The Fibonacci sequence is usually done recursively, and of course there are other methods. This is now learning to sell, using a PHP iterator to implement a Fibonacci sequence, with little difficulty, just rewrite the next () method in the class. Comments have been written into the code and are quite well understood.

<?php/** @author [Email protected]*/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 () {//Key here//Save the current value to  $newprevious        $newprevious = $this->current;//assigns the previous value and the current value to the current value        $this->current + = $this->previous;//Previous current value is assigned to the previous value        $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 + = = = =) break;} ?>

Program Run Result:

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610