MLP Autosync Terms

mlp-autosync-terms.php

<?php
/**
 * Plugin Name: MLP Autosync Terms
 * Description: Automatically sync all linked terms when a post is saved
 * Author:      Biont
 * Author URI:  https://github.com/Biont
 * License:     GPLv3
 */

/**
 * Class MLP_Sync_Terms
 */
class MLP_Sync_Terms {

	/**
	 * @var array All taxonomies that should be handled by this class
	 */
	private $allowed_taxonomies = array(
		'category'
	);

	/**
	 * @var array
	 */
	private $excluded_post_types = array(
		'attachment',
		'revision'
	);

	/**
	 * Class constructor. Set class variables
	 */
	public function __construct() {

		$this->current_blog_id = get_current_blog_id();

	}

	/**
	 * Register hooks
	 */
	public function register() {

		add_action( 'wp_insert_post', array( $this, 'wp_insert_post' ), 10, 3 );
	}

	/**
	 * Contains the post saving logic to transfer post meta and categories
	 *
	 * @wp-hook wp_insert_post
	 *
	 * @param          $post_ID
	 * @param \WP_Post $post
	 * @param          $update
	 */
	public function wp_insert_post( $post_ID, \WP_Post $post, $update ) {

		if ( in_array( $post->post_type, $this->excluded_post_types ) ) {
			return;
		}

		/**
		 * MLP switches blogs and saves remote posts. Check if we're still on the source blog (and dealing with the source post)
		 */
		if ( $this->current_blog_id !== get_current_blog_id() ) {
			return;
		}

		/**
		 * Now grab all linked posts. Bail if none are found
		 */
		$linked_posts = mlp_get_linked_elements( $post_ID, 'post', $this->current_blog_id );

		if ( empty( $linked_posts ) ) {
			return;
		}

		foreach ( $linked_posts as $blog_ID => $remote_post_ID ) {

			/**
			 * No need to sync with itself
			 */
			if ( $blog_ID == $this->current_blog_id ) {
				continue;
			}

			$this->sync_terms(
				$this->current_blog_id,
				$post_ID,
				$blog_ID,
				$remote_post_ID
			);

		}

	}

	/**
	 * Transfer terms from one post/blog to another
	 *
	 * @param $source_blog_id
	 * @param $source_post_id
	 * @param $target_blog_id
	 * @param $target_post_id
	 */
	private function sync_terms( $source_blog_id, $source_post_id, $target_blog_id, $target_post_id ) {

		$original_blog_id = get_current_blog_id();

		if ( $original_blog_id !== $source_blog_id ) {
			switch_to_blog( $source_blog_id );
		}

		$tax_and_terms = array();
		foreach ( $this->allowed_taxonomies as $tax ) {
			$tax_and_terms[ $tax ] = $this->get_linked_terms( $source_post_id, $tax );
		}

		switch_to_blog( $target_blog_id );
		foreach ( $tax_and_terms as $tax => $linked_terms ) {

			if ( empty( $linked_terms ) ) {
				continue;
			}
			$remote_terms = array();
			foreach ( $linked_terms as $source_TTID => $remote_TTIDs ) {
				if ( empty( $remote_TTIDs[ $target_blog_id ] ) ) {
					continue;
				}
				$remote_terms[] = $remote_TTIDs[ $target_blog_id ];
			}
			wp_set_object_terms( $target_post_id, $remote_terms, $tax );
		}

		switch_to_blog( $original_blog_id );

	}

	/**
	 * Collects all linked terms for a given taxonomy. The resulting array has the following structure:
	 *
	 * array(
	 *       $term_taxonomy_id => array( $blog_id => $remote_term_taxonomy_id )
	 * )
	 *
	 * @param $post_id
	 * @param $taxonomy
	 *
	 * @return array
	 */
	private function get_linked_terms( $post_id, $taxonomy ) {

		$result     = array();
		$categories = wp_get_post_terms( $post_id, $taxonomy );

		foreach ( $categories as $cat ) {
			$temp = array();

			$temp[ $this->current_blog_id ] = $cat->term_taxonomy_id;

			$linked_terms = mlp_get_linked_elements( $cat->term_taxonomy_id, 'term' );
			unset( $linked_terms[ $this->current_blog_id ] );

			foreach ( $linked_terms as $blog_id => $tt_id ) {
				$temp[ $blog_id ] = $tt_id;

			}

			$result[ $cat->term_taxonomy_id ] = $temp;
		}

		return $result;
	}
}

if ( is_admin() ) {
	add_action( 'inpsyde_mlp_loaded', 'mlp_sync_terms_init' );
}

/**
 * Initialize this plugin
 */
function mlp_sync_terms_init() {

	$mlp_sync_terms = new MLP_Sync_Terms();
	$mlp_sync_terms->register();
}