How to Build a WordPress Plugin for Single Site and Multisite Installations

When developing a WordPress plugin, one key decision you may face is whether to support both Plugin for Single Site and multisite installations. Multisite is a network of sites under a single WordPress installation, which can introduce complexities that your plugin must account for. Creating a plugin requires analyzing fundamental aspects needed to operate smoothly across these two environments.

Understanding the Multisite Environment

It is crucial to understand what a multisite is and how it differs from a single-site installation. In a single site setup, you have one website with its database tables. In contrast, a multisite installation shares the same database and tables across multiple sites, with each site identified by a unique site ID.

Key Differences

1. Database Structure: Multisite uses a shared database with a prefix for each site’s tables (e.g., wp_1_posts, wp_2_posts). It means that all sites in the network share the same database but have separate tables for their content.
2. User Management: Users can be assigned to multiple sites, and their capabilities may vary depending on the site. For example, a user might be an administrator on one site and a subscriber on another.
3. Settings Storage: Settings can be stored at the network level or site level, requiring different functions for retrieval and storage. This distinction is crucial for ensuring that your plugin behaves correctly in both environments.
4. Plugin Activation: Plugins can be activated network-wide or at individual sites. This process affects how you manage settings and data storage.

1. Checking for Multisite

The first step in building a plugin that supports both environments is to check if the current installation is multisite. You can use the is_multisite() function to determine this:

if (is_multisite()) {

    // Code for multisite

} else {

    // Code for single-site

}

This check allows you to conditionally execute code based on the environment, ensuring that your plugin behaves appropriately in both contexts.

Example of Conditional Logic

Here’s a simple example of how you might structure your plugin to handle both single site and multisite installations:

function my_plugin_function() {

    if (is_multisite()) {

        // Handle multisite-specific logic

        $sites = get_sites();

        foreach ($sites as $site) {

            switch_to_blog($site->blog_id);

            // Perform actions for each site

            restore_current_blog();

        }

    } else {

        // Handle single-site logic

        // Perform actions for the single site

    }

}

2. Data Storage Considerations

Network-Wide vs Site-Specific Settings

When storing settings, you need to decide whether they should be network-wide or site-specific. Use the following functions based on your requirements:

• Network-Wide Settings: Use update_site_option() to store settings that should apply to all sites in the network. It is useful for settings that affect the entire multisite installation.

update_site_option('my_plugin_setting', $value);

• Site-Specific Settings: Use update_option() for settings that are unique to each site. It is essential for configurations that should differ from one site to another.

1update_option('my_plugin_setting', $value);

Handling Data Storage

When saving data, ensure that you are using the correct functions based on the context. For example, if your plugin stores user preferences, you may want to save them in the user meta table using update_user_meta(), which works in both single site and multisite environments.

Example of Data Storage

Here’s an example of how to store settings based on the environment:

function my_plugin_save_settings($settings) {

    if (is_multisite()) {

        // Save network-wide settings

        update_site_option('my_plugin_network_setting', $settings);

    } else {

        // Save site-specific settings

        update_option('my_plugin_site_setting', $settings);

    }

}

3. User Management and Capabilities

User management can become complex in a multisite environment. Users can have different roles and capabilities on different sites. Therefore, it’s essential to validate assumptions about user capabilities and site switching.

User Capabilities

When checking user capabilities, use the current_user_can() function, which respects the context of the current site:

if (current_user_can('manage_options')) {

    // User has the capability to manage options

}

Site Switching

If your plugin allows users to switch between sites, ensure that you handle site switching gracefully. Use the switch_to_blog() function to switch the context to another site temporarily:

switch_to _blog($site_id);

// Perform actions on the switched site

restore_current_blog(); // Switch back to the original site

Example of User Management

Here’s an example of how to manage user capabilities in a multisite environment:

function my_plugin_user_capabilities() {

    if (is_multisite()) {

        $current_user = wp_get_current_user();

        if (user_can($current_user->ID, 'administrator')) {

            // User is an admin on the current site

        }

    } else {

        // Single-site user management

        if (current_user_can('administrator')) {

            // User is an admin

        }

    }

}

4. Network Activation

If your plugin is intended to be activated across the entire network, consider implementing network activation. This process allows the plugin to be activated for all sites in the network simultaneously.

Handling Network Activation

You can check if your plugin is network-activated by using the is_plugin_active_for_network() function. It is useful for setting up default options or performing actions that should only occur once for the entire network.

if (is_plugin_active_for_network('my-plugin/my-plugin.php')) {

    // Code for network activation

}

Example of Network Activation

Here’s how you might handle network activation in your plugin:

function my_plugin_network_activation() {

    if (is_multisite()) {

        // Set default options for all sites

        $default_setting = 'default_value';

        update_site_option('my_plugin_network_setting', $default_setting);

    }

}

register_activation_hook(__FILE__, 'my_plugin_network_activation');

5. Testing on Both Plugin for Single Site and Multisite Setups

One of the most critical steps in developing a plugin that supports both environments is thoroughly test. Ensure that you test your plugin in both single site and multisite installations to identify any issues that may arise.

Testing Checklist

• Functionality: Verify that all features work as expected in both environments.
• Data Storage: Check that settings are stored correctly based on the context (network vs. site).
• User Capabilities: Test user roles and capabilities to ensure they function correctly.
• Performance: Monitor performance to ensure that the plugin does not slow down either type of installation.

Example of Testing

You can create a testing function to verify that your plugin behaves correctly in both environments:

function my_plugin_test() {

    if (is_multisite()) {

        // Test multisite functionality

        $sites = get_sites();

        foreach ($sites as $site) {

            switch_to_blog($site->blog_id);

            // Perform tests for each site

            restore_current_blog();

        }

    } else {

        // Test single-site functionality

        // Perform tests for the single site

    }

}

Frequently Asked Questions

Conclusion

The development of WordPress plugins to serve single site and multisite environments needs strategic planning of data storage methods alongside user management protocols and testing protocols. Your plugin will deliver a smooth user experience to all users if you use proper functions alongside best practices. Always remember to test thoroughly in both environments to ensure compatibility and functionality. With these considerations in mind, you’ll be well on your way to developing a robust and versatile WordPress plugin.

About the writer

Hassan Tahir wrote this article, drawing on his experience to clarify WordPress concepts and enhance developer understanding. Through his work, he aims to help both beginners and professionals refine their skills and tackle WordPress projects with greater confidence.