Unique_WP_Query.php

gistfile1.txt

<?php
/**
 * Wrapper for WP_Query
 * Interacts directly with WP_Query_Manager to ensure
 * only unique posts are ever returned.
 *
 * Known issues:
 * Won't work with offset values
 */
class Unique_WP_Query extends WP_Query {
	function __construct( $args ) {
		// Act as a flag for pre_get_posts
		$args['unique_wp_query'] = true;

		// Initialize the WP_Query object like normal
		parent::__construct( $args );

		// Track used posts, and remove duplicates
		Unique_WP_Query_Manager::process_posts( $this->posts, $this->post_count, $this->get( 'original_posts_per_page' ) );
	}
}

/**
 * Keeps track of which posts have already appeared and
 * removes them from future Unique_WP_Query objects.
 */
class Unique_WP_Query_Manager {

	/**
	 * Keep track of which post_ids have already been used
	 * @var array
	 */
	public static $used_post_ids = array();

	/**
	 * Keeps track of how many used_posts_ids exist
	 * @var integer
	 */
	public static $used_post_count = 0;

	/**
	 * Takes the posts and post count of a WP_Query object and
	 * ensures that it removes posts that have already been used,
	 * and then trims it to the necessary size.
	 *
	 * @param array &$posts
	 * @param integer &$post_count
	 */
	public static function process_posts( &$posts, &$post_count, $original_posts_per_page ) {

		// Keep track of how many posts are acceptable to return
		$current_accepted_post_count = 0;

		// Make sure we have posts
		if ( empty( (array) $posts ) ) {
			return;
		}

		// Loop through all the found posts
		foreach ( (array) $posts as $key => $post ) {

			// If we have enough acceptable posts, break the loop
			// Otherwise, determine if we've already used this post
			if ( $original_posts_per_page > $current_accepted_post_count ) {

				// Has this post already been used?
				if ( in_array( $post->ID, Unique_WP_Query_Manager::$used_post_ids ) ) {
					// Remove from $posts
					unset( $posts[ $key ] );

					// And update count
					$post_count--;

				} else {
					// If not, add it to the list of used ids
					Unique_WP_Query_Manager::$used_post_ids[] = $post->ID;

					// Update how many accepted posts we have
					$current_accepted_post_count++;
				}
			} else {
				// If we have enough acceptable posts, break the foreach
				// This prevents extra results from accidently being added to $used_post_ids
				break;
			}
		}

		// Reindex the array correctly
		$posts = array_values( $posts );

		// Update the $used_post_count
		Unique_WP_Query_Manager::$used_post_count = count( Unique_WP_Query_Manager::$used_post_ids );

		// Trim any excess posts and update $post_count
		if ( count( $posts ) > $original_posts_per_page ) {

			// Remove extra posts
			$posts = array_slice( $posts, 0, $original_posts_per_page );

			// Update post count to our new value
			$post_count = $original_posts_per_page;
		}
	}
}

if ( ! function_exists( 'unique_wp_query_pre_get_posts' ) ) {
	/**
	 * Increase the posts_per_page value by the number of posts that have
	 * already been used. Executes as the last pre_get_posts action.
	 */
	function unique_wp_query_pre_get_posts( &$query ) {

		// Only apply to Unique_WP_Query objects
		if ( true === $query->get( 'unique_wp_query' ) ) {

			// Check our upward bound of posts_per_page
			$posts_per_page = $query->get( 'posts_per_page' );
			if ( $posts_per_page <= 200 ) {
				// Increase posts_per_page by the amount of used post_ids
				$query->set( 'original_posts_per_page', $posts_per_page );
				$query->set( 'posts_per_page', $posts_per_page + Unique_WP_Query_Manager::$used_post_count );
			} else {
				// Max out at 200 posts_per_page
				$query->set( 'original_posts_per_page', 200 );
				$query->set( 'posts_per_page', 200 );
			}
		}
	}

	// Ensure it's always the last pre_get_posts action
	add_action( 'pre_get_posts', 'unique_wp_query_pre_get_posts', PHP_INT_MAX );
}