wp-db-merge

Merge a single site database into a multi site database

Setup:

1. Fill out $options['connection']
2. Fill out $options['databases'] where single is a non-multisite WordPress database and multisite is a multisite WordPress database
3. Create new site/blog using wp gui on the multisite, record the newly created blog ID
4. Fill in $options['data']['blog_id'] with the previously recorded blog ID
5. Fill out $options['data']['mariadb_extra_file'] with the path to your mariadb defaults extra file for authentication
6. Set $options['data']['output_author_sql'] to true or false to force the sql that updates post_author to be written to a file for execution later.
7. Set $options['data']['name'] to an arbitrary name.
8. Run merge.php using the php executable

Caution:

Create backups of your databases before using this tool!