While updating my Check Amazon Links plugin to work with WordPress Multisite, I struggled with how I could make my plugin settings universal across all network installs.  More specifically, I wanted it to be an option that could be turned on and off.  I tried to find a way to implement a hook or filter for when the plugin options were being updated via the settings page, but I had so much trouble with that, that I finally decided to use some Javascript.  Yay for javascript!  Sometimes it’s the easier option.

First, I added the option to my settings page, but only on multisite installs.  Here’s what it looks like:

Next, I wrote the Javascript (jQuery) code to respond to submit events:

jQuery(document).ready(function () {
    var option_page_name = jQuery('input[name=option_page]').val();
    if (typeof(option_page_name) != "undefined") {
        if(option_page_name === 'amazon_link_plugin_options') {
            jQuery('form').submit(function(e) {
                var update_all = jQuery('select[name="azlc_multisite_same[toggle]"]').val();
                if(update_all === '1') {
                    jQuery.post(ajaxurl, 'action=azlc_ms', function(){});
                }

            });
        }
    }

});

As you see, my code checks the page name to insure that it only sends the AJAX request if it’s MY plugin’s page.   I add that javascript code to a javascript file I already enqueue.

Here’s the PHP WordPress Backend code for handling the Ajax request:

if(is_multisite()) {
	add_action('wp_ajax_azlc_ms', 'azlc_ms');
}

function azlc_ms() {
	add_site_option( 'azlc_update_from', get_current_blog_id() );
}

And here’s the PHP WordPress code the updates the options:

if(is_multisite()) {
	add_action('plugins_loaded', 'azlc_multisite');
}


function azlc_multisite() {
	global $wpdb;

	// check for flag 
        // I call this a flag because its existence means that this code needs to run.
        // You could write this to make it more human readable
	$blog_id = get_site_option('azlc_update_from');
	if($blog_id) {
		// switch to the blog to copy the actions from
		switch_to_blog($blog_id);
		$options = get_option('azlc_plugin_options');
		// copy settings to all sites
		AmazonLinkCheckerCore::copy_settings_from($blog_id, 'azlc_plugin_options', $options );
		// remove flag
		delete_site_option('azlc_update_from');
		// switch back
		restore_current_blog();
	}
}

And here’s the code that actually does the copying:

	public static function copy_settings_from($source_id, $option_name, $option_value) {
				global $wpdb;
				$sql = "SELECT blog_id FROM $wpdb->blogs";
				$blog_ids = $wpdb->get_col($sql);
				foreach($blog_ids as $blog_id) {
					// update option on other blogs
					if($blog_id!=$source_id) {
						switch_to_blog($blog_id);
						update_option($option_name, $option_value);
					}
				}
				restore_current_blog();
	}

Related Tutorial

Don’t miss this related article: How to Enable WordPress Multisite for your Plugin

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I write this blog with sincere hope that I can help other WordPress developers.  Please let me know if this helped you, or if I made a bad error.  Thanks!