Migrate Wordpress Terms and Tags from one taxonomy to another.

wordpress-migrate-terms-from-taxonomy-to-taxonomy.php

/**
 * WP-CLI command to move terms associated with a specific custom post type from one taxonomy to another.
 *
 * Usage: wp move-terms --source=old_taxonomy --target=new_taxonomy --post_type=my_custom_post_type
 */

/**
 * Moves terms from one taxonomy to another for a specific custom post type.
 *
 * ## OPTIONS
 *
 * --source=<source_taxonomy>
 * : The source taxonomy slug.
 *
 * --target=<target_taxonomy>
 * : The target taxonomy slug.
 *
 * --post_type=<post_type>
 * : The custom post type slug.
 *
 * ## EXAMPLES
 *
 *     wp move-terms --source=old_taxonomy --target=new_taxonomy --post_type=my_custom_post_type
 *
 * @when after_wp_load
 */
function wpcli_move_terms( $args, $assoc_args ) {
  $source_taxonomy = $assoc_args['source'];
  $target_taxonomy = $assoc_args['target'];
  $post_type       = $assoc_args['post_type'];

  // Get all terms from the source taxonomy.
  $terms = get_terms( array(
      'taxonomy'   => $source_taxonomy,
      'hide_empty' => false,
  ) );

  // If no terms found, display a message and exit.
  if ( is_wp_error( $terms ) || empty( $terms ) ) {
      WP_CLI::warning( 'No terms found in the source taxonomy.' );
      return;
  }

  $term_mapping = array();

  foreach ( $terms as $term ) {
      // Get all posts of the specific post type associated with the current term in the source taxonomy.
      $posts = get_posts( array(
          'post_type'   => $post_type,
          'numberposts' => -1,
          'tax_query'   => array(
              array(
                  'taxonomy' => $source_taxonomy,
                  'field'    => 'term_id',
                  'terms'    => $term->term_id,
              ),
          ),
      ) );

      // If no posts found for this term, skip to the next term.
      if ( empty( $posts ) ) {
          continue;
      }

      // Check if the term already exists in the target taxonomy.
      $target_term = term_exists( $term->name, $target_taxonomy );

      // If the term doesn't exist in the target taxonomy, create it.
      if ( !$target_term ) {
          $new_term = wp_insert_term(
              $term->name,
              $target_taxonomy,
              array(
                  'description' => $term->description,
                  'slug'        => $term->slug,
                  'parent'      => $term->parent,
              )
          );

          if ( is_wp_error( $new_term ) ) {
              WP_CLI::warning( "Failed to create term '{$term->name}' in the target taxonomy." );
              continue;
          }

          $target_term_id = $new_term['term_id'];
      } else {
          $target_term_id = $target_term['term_id'];
      }

      // Map source term ID to target term ID.
      $term_mapping[$term->term_id] = $target_term_id;

      // Assign the posts to the term in the target taxonomy.
      foreach ( $posts as $post ) {
          wp_set_post_terms( $post->ID, $target_term_id, $target_taxonomy, true );
      }

      // Optional: Delete the term from the source taxonomy.
      wp_delete_term( $term->term_id, $source_taxonomy );

      WP_CLI::success( "Term '{$term->name}' moved from '{$source_taxonomy}' to '{$target_taxonomy}' for post type '{$post_type}'." );
  }

  WP_CLI::success( "Terms successfully moved from '{$source_taxonomy}' to '{$target_taxonomy}' for post type '{$post_type}'." );
}

// Register the WP-CLI command.
if ( defined( 'WP_CLI' ) && WP_CLI ) {
  WP_CLI::add_command( 'move-terms', 'wpcli_move_terms' );
}