Class to extended WordPress' 3.0.x WP_Query to allow sorting by a meta_key.

posts-ordered-by-meta.php

<?php
/*
    PostsOrderedByMetaQuery class that extends WP_Query and sorts posts meta_key

    Author: Mike Schinkel (http://mikeschinkel.com)

    This example works, just drop into the root of your website and call directly.
    Use the class in your plugins or themes.

    See: http://stackoverflow.com/questions/4111255/how-to-sort-a-query-posts-function-by-custom-field-while-limiting-posts-by-ano

*/

header('Content-type:text/plain');
include "../wp-load.php";

class PostsOrderedByMetaQuery extends WP_Query {
  var $posts_ordered_by_meta = true;
  var $orderby_order = 'ASC';
  var $orderby_meta_key;
  function __construct($args=array()) {
    add_filter('posts_join',array(&$this,'posts_join'),10,2);
    add_filter('posts_orderby',array(&$this,'posts_orderby'),10,2);
    $this->posts_ordered_by_meta = true;
    $this->orderby_meta_key = $args['orderby_meta_key'];
    unset($args['orderby_meta_key']);
    if (!empty($args['orderby_order'])) {
      $this->orderby_order = $args['orderby_order'];
      unset($args['orderby_order']);
    }
    parent::query($args);
  }
  function posts_join($join,$query) {
    if (isset($query->posts_ordered_by_meta)) {
      global $wpdb;
      $join .=<<<SQL
INNER JOIN {$wpdb->postmeta} postmeta_price ON postmeta_price.post_id={$wpdb->posts}.ID
       AND postmeta_price.meta_key='{$this->orderby_meta_key}'
SQL;
    }
    return $join;
  }
  function posts_orderby($orderby,$query) {
    if (isset($query->posts_ordered_by_meta)) {
      global $wpdb;
      $orderby = "postmeta_price.meta_value {$this->orderby_order}";
    }
    return $orderby;
  }
}

$thirtydays = date('Y/m/d', strtotime('+30 days'));
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$query = new PostsOrderedByMetaQuery(array(
  'post_type' => array('post', 'real-estate'),
  'meta_key' => 'Time Available',
  'meta_compare' => '<=',
  'meta_value' => $thirtydays,
  'paged' => $paged,
  'orderby_meta_key' => 'Price',
  'orderby_order'    => 'DESC',
));
foreach($query->posts as $post) {
  echo " {$post->post_title}\n";
}

dude you're amazing oO'