Migrate stand-alone WordPress Site to a MultiSite sub-site

# Documentation: Moving a Standalone WordPress Site to a MultiSite Sub-Site

This guide outlines the steps to migrate a standalone WordPress site to a sub-site within a WordPress MultiSite installation. It assumes you already have the sub-site set up on the MultiSite instance.

### Prerequisites:
- Existing WordPress MultiSite network.
- A standalone WordPress site that you want to migrate.
- Access to both the phpMyAdmin of the standalone site and the MultiSite installation.
- Access to both the file systems of the standalone site and the MultiSite installation.

### Steps:

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### **Step 1: Export the Standalone Site Database**

1. **Access phpMyAdmin**:
   Go to the hosting server where the standalone WordPress site is hosted. Log in to phpMyAdmin.

2. **Export the Database**:
   Select the database associated with the standalone WordPress site and export it in SQL format.

   - Choose "Quick Export" for simplicity, or "Custom Export" if you need specific configurations (recommended: ensure "Add DROP TABLE" option is selected).

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### **Step 2: Import Database into the MultiSite Instance**

1. **Access phpMyAdmin on the MultiSite Server**:
   Log in to phpMyAdmin on the MultiSite server.

2. **Import the Database**:
   Go to the correct database for your MultiSite setup. Select "Import" and upload the SQL file you exported from the standalone site.

3. **Change Table Prefixes**:
   After importing, you'll need to update the table prefixes to match the sub-site you are migrating into. For example, if your sub-site's ID is `2`, you'll need to rename all the tables with a prefix like `wp_2_`.

   To do this:
   - Rename the tables in phpMyAdmin to match the format `wp_2_` instead of the original `wp_`.
   - Update the table names for:
     - wp_posts → wp_2_posts
     - wp_postmeta → wp_2_postmeta
     - wp_options → wp_2_options
     - wp_users → (No change, as this table is shared across the network).
     - wp_usermeta → (No change).

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### **Step 3: Copy the Uploads Folder**

1. **Locate the Uploads Folder**:
   On the standalone site’s server, navigate to the `wp-content/uploads` directory.

2. **Copy Files to MultiSite Server**:
   On the MultiSite server, find the correct directory for the sub-site, which would be located at `/wp-content/uploads/sites/2/` (replace `2` with the correct site ID).

   - Copy all the files from the old site's `/uploads` directory to this new path.

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### **Step 4: Migrate Plugins and Themes**

1. **Migrate Plugins**:
   If your standalone site uses any plugins that are not present on the MultiSite instance, copy those plugins from the standalone site’s `/wp-content/plugins/` folder to the same folder on the MultiSite server.

2. **Migrate the Theme**:
   If the standalone site uses a custom or non-default theme, copy the theme folder from the standalone site’s `/wp-content/themes/` directory to the MultiSite server’s `/wp-content/themes/` folder.

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### **Step 5: Verify Site Functionality**

1. **Check Site URL**:
   Go to the URL of the newly migrated sub-site. For example, if the sub-site’s domain is `https://example.com/subsite`, you should now see the migrated site content.

2. **Test Functionality**:
   Verify that:
   - Posts and pages are displaying correctly.
   - Media files load without issues.
   - Plugins and themes are functioning as expected.

3. **Update Permalinks**:
   Log into the admin dashboard of the sub-site and navigate to **Settings** > **Permalinks**. Click “Save Changes” to regenerate the permalink structure.

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### **Troubleshooting Tips**:

- **Missing Media Files**:
   If images or media aren’t displaying, double-check that all files from the `uploads` folder have been copied to the correct sub-site directory (i.e., `/wp-content/uploads/sites/2`).

- **Database Connection Errors**:
   Ensure that the database table prefixes are correctly updated to match the MultiSite’s sub-site. For instance, for sub-site `2`, all WordPress tables should start with `wp_2_`.

- **Login Issues**:
   If you cannot log into the sub-site after migration, check the `wp_2_options` table for the correct `siteurl` and `home` values, as well as potential user account conflicts.

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### Conclusion:

By following these steps, you will successfully migrate a standalone WordPress site into a sub-site on your WordPress MultiSite network. If any issues arise during the migration process, review each step carefully, especially the database prefix changes and file locations.