jQuery Post Loader for WordPress Home Page

mfields.org-post-loader.php

<?php
/*
Plugin Name: mfields.org - Ajax Append Posts
Plugin URI: 
Description:
Version: 0.1.2
Author: Michael Fields
Author URI: http://mfields.org/
Copyright 2010 Michael Fields  michael@mfields.org
License GPLv2
*/


/**
 * Ensure that jQuery is included on the "posts" page.
 * @since 2010-12-06
 */
function mfields_ajax_append_posts_jquery() {
	if ( is_home() ) {
		wp_enqueue_script( 'jquery' );
	}
}
add_action( 'wp_print_scripts', 'mfields_ajax_append_posts_jquery' );


/**
 * Button to load more posts on the "posts" page.
 *
 * This action should be added to either home.php or index.php
 * and should be placed outside of the div that contains posts.
 *
 * @param     string    Text to display inside the button.
 * @param     string    Add before the button.
 * @param     string    Add after the button.
 * @return    void
 *
 * @since 2010-12-06
 */
function mfields_ajax_append_posts_button( $text = '%s more posts.', $before = '', $after = '' ) {
	if( is_home() ) {
		$posts_remaining = '';
		if( isset( $GLOBALS['wp_query']->found_posts ) && isset( $GLOBALS['wp_query']->post_count ) ) {
			$posts_remaining = (int) $GLOBALS['wp_query']->found_posts - (int) $GLOBALS['wp_query']->post_count;
		}
		$text = sprintf( $text, '<span id="posts-remaining">' . $posts_remaining . '</span>' );
		print $before . '<span id="load-posts">' . $text . '</span>' . $after;
	}
}
add_action( 'mfields_ajax_append_posts_button', 'mfields_ajax_append_posts_button' );


/**
 * Public Ajax Callback.
 *
 * Simulate the WordPress loop during an Ajax call.
 *
 * You can call this function using the following urls:
 *  1. /wp-admin/admin-ajax.php?action=mfields_append_posts
 *  2. /wp-admin/admin-ajax.php?action=mfields_append_posts&paged=2
 * 
 * @return void.
 *
 * @since 2010-12-06
 * @todo Add support for other multiple views.
 */
function mfields_ajax_append_posts_query() {
	$response = array(
		'html'  => 'none',
		'count' => 0
		);
	$query = array(
		'post_type'   => 'post',
		'post_status' => 'publish'
		);
	if ( isset( $_GET['paged'] ) ) {
		$query['paged'] = absint( $_GET['paged'] );
	}
	query_posts( $query );
	if( have_posts() ) {
		ob_start();
		while( have_posts() ) {
			the_post();
			the_title( '<h2>', '</h2>' );
			the_content();
			$response['count']++;
		}
		$response['html'] = ob_get_contents();
		ob_end_clean();
	}
	print json_encode( $response );
	exit;
}
add_action( 'wp_ajax_mfields_append_posts', 'mfields_ajax_append_posts_query' );
add_action( 'wp_ajax_nopriv_mfields_append_posts', 'mfields_ajax_append_posts_query' );


/**
 * Print javascript to the footer of the "posts" page.
 *
 * @return void.
 *
 * @todo fine-tune.
 * @todo minify.
 * 
 * @since 2010-12-06
 */
function mfields_ajax_append_posts_js() {
	if ( is_home() ) {
		$args = array(
			'url'   => admin_url( 'admin-ajax.php' ),
			'total' => 0
			);
		if ( isset( $GLOBALS['wp_query']->found_posts ) ) {
			$args['found_posts'] = absint( $GLOBALS['wp_query']->found_posts );
		}
		print <<< EOF
<script type="text/javascript">
jQuery( document ).ready( function( $ ) {
	
	var next_page       = 2;
	var total_posts     = {$args['found_posts']};
	var posts_in_dom    = $( '#content .hentry' ).length;
	var posts_remaining = total_posts - posts_in_dom;
	var button          = $( '#load-posts' );
	var container       = $( '#content' );
	
	button.click( function () {
		$.ajax( {
			url      : '{$args['url']}',
			data     : { 'action' : 'mfields_append_posts', 'paged' : next_page },
			type     : 'GET',
			dataType : 'json',
			cache    : false,
			success  : function( response ) {
				if ( 0 === response.count ) {
					button.remove();
				}
				else {
					container.append( response.html );
					posts_in_dom    = posts_in_dom + parseInt( response.count );
					posts_remaining = total_posts - posts_in_dom;
					if ( 0 === posts_remaining ) {
						button.remove();
					}
					else {
						$( '#posts-remaining' ).text( posts_remaining );
						next_page++;
					}
				}
			}
		} );
	} );
});
</script>
EOF;
	}
}
add_action( 'wp_footer', 'mfields_ajax_append_posts_js' );