WordPress post iterator

wp_post_iterator.php

<?php
/* Iterator for arrays of WordPress posts or `WP_Query`. 
 *
 * Simplifies "the loop" by automatically handling the `$post` global for each iteration 
 * (calling `the_post()`, `setup_postdata()` etc.) and makes sure to reset the global state when the loop has finished. 
 *
 * Usage:
 * Loop over ten last posts:
 * <?php foreach (new WPQueryIterator(array('post_type' => 'post', 'posts_per_page' => 10)) as $i => $p): ?>
 *    <?php the_title(); ?>
 *    <?php the_excerpt(); ?>
 *    <?php the_content(); // etc. ?>
 * <?php endforeach; ?>
 * 
 * Iterator objects are proxies for WP_Query methods and properties:
 * <?php $q = new WPQueryIterator(); ?>
 * <?php $post_count = $q->found_posts; ?>
 * 
 * Use `WPPostIterator` for arrays of posts (returned from SQL queries).
 * 
 * Compare to the "classic" way:
 * <?php $q = new WP_Query(array('post_type' => 'post', 'posts_per_page' => 10)) ?>
 * <?php $i = 0; ?>
 * <?php while($q->have_posts()): ?>
 *    <?php $q->the_post() ?>
 *    <?php the_title(); ?>
 *    <?php the_excerpt(); ?>
 *    <?php the_content(); // etc. ?>
 *    <?php $i++; ?>
 * <?php endwhile; ?>
 * <?php wp_reset_postdata() ?>
 */
class WPPostIterator implements Iterator {
	protected $index = 0;
	
	public function __construct($posts) {
		global $post;
		$this->original_post = $post;
		$this->posts = $posts;
	}
	
	function rewind() {
		$this->index = 0;
		$this->current();
	}
	
	function current() {
		if (!isset($this->posts[$this->key()]))
			return NULL;
		$current_post = $this->posts[$this->index];
		$GLOBALS['post'] = $current_post;
		setup_postdata($current_post);
	    return $current_post;
	}
	
	function key() {
	    return $this->index;
	}
	
	function next() {
		$this->index++;
		$valid = isset($this->posts[$this->key()]);		
	}
	
	function valid() {
		$valid = isset($this->posts[$this->key()]);
		if (!$valid) {
			wp_reset_query();
			wp_reset_postdata();
			
			setup_postdata($this->original_post);
			$GLOBALS['post'] = $this->original_post;
		}
			
		return $valid;
	}
}

class WPQueryIterator extends WPPostIterator {
	protected $query = NULL;
	
	public function __construct($query_arguments = array()) {
		global $post;
		$this->query = new WP_Query($query_arguments);
		parent::__construct($this->query->posts);
	}
	
	// act as proxy for WP_Query
	public function __call($method, $arguments) {
		if (method_exists($this->query, $method))
			return call_user_func_array(array($this->query, $method), $arguments);
	}
	
	public function __get($property) {
		if (isset($this->query->$property))
			return $this->query->$property;
		
	}
}