As mentioned in the answer of RRikesh, a multiside installation make it all easier because it's the same database and you have access to it.
If you have problems connectiing to the foreign database (maybe some security restrictions or the database is not on the same server), you have to do a bit more work. In this case, you can fetch the feed, parse and store it.
Fetching the feed is a bit problematic because the feed normally returns the latests x posts (default is 10 posts). If you want to fetch a feed with all posts, you have to install a "server" plugin which modify the settings. To not disturb the normal feed behaviour, I trigger the unlimited feed with a url parameter. Let's start with the "server" plugin.
/**
* Plugin Name: Fetch Posts Server
* Plugin URI:
* Description: Allow to fetch all posts in XML format from another blog
* Version: 0.1
* Author: Ralf Albert
* Author URI: http://yoda.neun12.de
* License: GPLv3
*/
namespace FetchPostsServer;
add_filter(
'query_vars',
function( $qvars ) {
array_push( $qvars, 'getall' );
return $qvars;
}
);
add_action( 'pre_get_posts', __NAMESPACE__ . '\get_all_posts_as_xml' );
function get_all_posts_as_xml( $query ) {
if ( true === $query->is_feed ) {
$getall = ( isset( $query->query['getall'] ) ) ? $query->query['getall'] : '';
if ( ! empty( $getall ) ) {
// remove the feed posts limit
add_filter(
'post_limits_request',
function( $limits ) { return ''; }
);
}
}
}
That's easy. At first the plugin add a query var. In the next step, the plugin hook into pre_get_posts, check if a feed is requested and check if the query var getall is set. If it is set, add a filter to remove the post limit.
If we now request a feed and pass the url parameter getall, we get all posts instead of the normally limited amount of 10 (or so).
On the "client" side, it is a bit more work. We need a cron to check for new posts, get all posts on the first run and return the stored posts if requested. I choose the options table to store the posts, I think it's the best place.
/**
* Plugin Name: Fetch Posts Client
* Plugin URI:
* Description: Fetch posts in XML format from another blog
* Version: 0.1
* Author: Ralf Albert
* Author URI: http://yoda.neun12.de
* License: GPLv3
*/
namespace FetchPostsClient;
// schedule event
if ( ! wp_next_scheduled( 'fetch_posts' ) ) {
wp_schedule_event( time(), 'daily', 'fetch_posts' );
}
add_action( 'fetch_posts', __NAMESPACE__ . '\fetch_posts' );
/*
* fetch the newest posts once a day
*/
function fetch_posts() {
fetch_posts_as_xml( array( 'url' => 'http://wpse.tld/', 'cat' => 'uncategorized', 'return' => false ) );
}
/*
* fetching the posts
*/
function fetch_posts_as_xml( $args, $return = false ) {
// for debugging
//add_filter( 'wp_feed_cache_transient_lifetime' , function() { return 5; } );
// get stored posts from options
$fetched_posts = get_option( 'fetched_posts' );
// if we just need the stored posts, return them
if ( true == $return || ( isset( $args['return'] ) && true == $args['return'] ) )
return $fetched_posts;
// prepare fetching the feed
if ( ! function_exists( 'fetch_feed' ) )
include_once( ABSPATH . WPINC . '/feed.php' );
if ( ! isset( $args['url'] ) )
return;
$url = $args['url'];
/*
* other options like author, tag, etc. possible
*/
// add category (if present)
if ( isset( $args['cat'] ) )
$url = add_query_arg( array( 'cat' => $args['cat'] ), $url );
// need the feed (rss2)
$url = add_query_arg( array( 'feed' => 'rss2' ), $url );
// for debugging
//printf( '<p>Posts stored: %d<br>', sizeof( $fetched_posts ) );
// if no posts are stored, this is the first run, get all posts
if( empty( $fetched_posts ) )
$url = add_query_arg( array( 'getall' => 1 ), $url );
// start fetching the feed
$rss = fetch_feed( $url );
if ( isset( $rss->errors ) && ! empty( $rss->errors ) ) {
// do some better error handling like logging the error
var_dump( $rss->errors );
return;
}
if ( ! is_wp_error( $rss ) ) {
$maxitems = $rss->get_item_quantity( -1 ); // get as much items as possible
$rss_items = $rss->get_items( 0, $maxitems );
}
// parsing the feed
foreach ( $rss_items as $item ) {
$fetched_posts[ $item->__toString() ] = array(
'title' => $item->get_title(),
'content' => $item->get_content(),
'permalink' => $item->get_permalink()
);
}
// for debugging
//printf( 'New postcount: %d</p>', sizeof( $fetched_posts ) );
// store posts in options
update_option( 'fetched_posts', $fetched_posts );
// return the posts
return $fetched_posts;
}
The plugin fetch the feed daily, parse the posts and store them in the options table. Displaying the stored posts is very easy:
$posts = FetchPostsClient\fetch_posts_as_xml( array(), true );
echo '<ol>';
array_walk(
$posts,
function( $post ) {
printf(
'<li><ul><li><a href="%s">%s</a></li><li>%s</li></ul></li>',
$post['permalink'],
$post['title'],
$post['content']
);
}
);
echo '</ol>';
The function returns an array with each single post as array (title, permalink and content). You can place the code in a template or widget.
Remark
This is "raw" code. It needs to be optimized, some values have to be sanitized and so on. Don't use it in your production or public blog!
