Copy Taxonomy Data WordPress

functions.php

// Define your source and target taxonomies, as well as the post type (optional)
$source_taxonomy = 'project-category'; // Source taxonomy
$target_taxonomy = 'project-tag'; // Target taxonomy
$post_type = 'project'; // Replace with your post type, or leave empty for all

// Function to copy terms from the source taxonomy to the target taxonomy
function copy_taxonomy_terms( $source_taxonomy, $target_taxonomy, $post_type = '' ) {
    // Step 1: Get all posts in the specified post type with terms from the source taxonomy
    $args = array(
        'post_type' => $post_type ?: 'any', // Use 'any' for all post types if not specified
        'posts_per_page' => -1,
        'post_status' => 'any',
        'tax_query' => array(
            array(
                'taxonomy' => $source_taxonomy,
                'field' => 'slug',
                'terms' => get_terms(array('taxonomy' => $source_taxonomy, 'fields' => 'slugs')),
                'operator' => 'IN',
            ),
        ),
    );

    $posts = get_posts( $args );

    // Step 2: Loop through each post to copy terms to the target taxonomy
    foreach ( $posts as $post ) {
        // Get the source terms for the current post
        $source_terms = wp_get_post_terms( $post->ID, $source_taxonomy, array( 'fields' => 'slugs' ) );

        if ( ! empty( $source_terms ) ) {
            // Step 3: Check if each term exists in the target taxonomy, and create if it doesn't
            foreach ( $source_terms as $term_slug ) {
                if ( ! term_exists( $term_slug, $target_taxonomy ) ) {
                    // If term does not exist, create it in the target taxonomy
                    $term = get_term_by( 'slug', $term_slug, $source_taxonomy );
                    wp_insert_term( $term->name, $target_taxonomy, array( 'slug' => $term_slug ) );
                }
            }

            // Step 4: Assign the terms to the target taxonomy for the post
            wp_set_post_terms( $post->ID, $source_terms, $target_taxonomy, false );
        }
    }
}

// Run the function on 'init' - Remember to remove this after running once
add_action( 'init', function() use ( $source_taxonomy, $target_taxonomy, $post_type ) {
    copy_taxonomy_terms( $source_taxonomy, $target_taxonomy, $post_type );
});