Code snippets from #wcla talk "Developing for MultiSite"

gistfile1.php

/*
 * Knowing where you are
 */


 is_multisite()
 http://codex.wordpress.org/Function_Reference/is_multisite

 is_main_site()
 http://codex.wordpress.org/Function_Reference/is_main_site

 is_admin()
 http://codex.wordpress.org/Function_Reference/is_admin

 is_network_admin()
 http://codex.wordpress.org/Function_Reference/is_network_admin

/*
 * Knowing who you are
 */
 
 is_super_admin()
 http://codex.wordpress.org/Function_Reference/is_super_admin

 is_user_logged_in()
 http://codex.wordpress.org/Function_Reference/is_user_logged_in

 // returns an object with infomation about the current user
 $current_user = wp_get_current_user();
 http://codex.wordpress.org/Function_Reference/wp_get_current_user

 // test for specific capabilities for the current user
 if( current_user_can( ‘edit_themes’ ) )
 http://codex.wordpress.org/Function_Reference/current_user_can
 
/*
 * What Sub-Site are we in?
 */
 
 global $blog_id;
 
 $id = get_current_blog_id();
 http://codex.wordpress.org/Function_Reference/get_current_blog_id
 
 $details = get_blog_details( $id );
 http://codex.wordpress.org/Function_Reference/get_blog_details
 
/* 
 * URL Functions
 */
 
 home_url( $path );
 http://codex.wordpress.org/Function_Reference/home_url

 site_url( $path );
 http://codex.wordpress.org/Function_Reference/site_url
 
 admin_url( $path );
 http://codex.wordpress.org/Function_Reference/admin_url
 
 network_home_url( $path );
 http://codex.wordpress.org/Function_Reference/network_home_url

 network_site_url( $path );
 http://codex.wordpress.org/Function_Reference/network_site_url
 
 network_admin_url( $path );
 http://codex.wordpress.org/Function_Reference/network_admin_url
 
 $url = get_home_url( $blog_id );
 http://codex.wordpress.org/Function_Reference/get_admin_url

 $url = get_site_url( $blog_id );
 http://codex.wordpress.org/Function_Reference/get_admin_url

 $url = get_admin_url( $blog_id );
 http://codex.wordpress.org/Function_Reference/get_admin_url
 
/*
 * WP Constants
 */
 http://codex.wordpress.org/Determining_Plugin_and_Content_Directories
 http://codex.wordpress.org/Editing_wp-config.php
 
 WP_CONTENT_DIR
 WP_CONTENT_URL
 
 WP_PLUGIN_DIR
 WP_PLUGIN_URL
 
 WPMU_PLUGIN_DIR
 WPMU_PLUGIN_URL

/*
 * Site-by-Site Options
 */
 
 // manipulate options for the blog you are currently in
 // works for single site install or any single site in the network
 
 add_option( $option , $value );
 http://codex.wordpress.org/Function_Reference/add_option

 update_option( $option , $value );
 http://codex.wordpress.org/Function_Reference/update_option

 get_option( $option );
 http://codex.wordpress.org/Function_Reference/get_option

 // manipulate options for a specific blog
 
 add_blog_option( $blog_id , $option , $value );
 http://codex.wordpress.org/Function_Reference/add_blog_option

 update_blog_option( $blog_id , $option , $value );
 http://codex.wordpress.org/Function_Reference/update_blog_option

 get_blog_option( $blog_id , $option );
 http://codex.wordpress.org/Function_Reference/get_blog_option
 
/* 
 * Network Options
 */
 
 add_site_option( $option , $value );
 http://codex.wordpress.org/Function_Reference/get_blog_option

 update_site_option( $option , $value );
 http://codex.wordpress.org/Function_Reference/get_blog_option

 get_site_option( $option );
 http://codex.wordpress.org/Function_Reference/get_blog_option

/* 
 * Adding Menus
 */
 
 // adds a menu and settings page to the admin menu in a single site 
 add_action( ‘admin_menu’ , ‘add_my_menu’ );

 // adds a menu to the network admin area
 add_action( ‘network_admin_menu’ , ‘add_my_menu’ );

 // callback funtion that actually adds the menus
 function add_my_menu() {
     add_menu_page( $page_title , $menu_title , $capability , $menu_slug , $function , $icon_url , $position );
     add_submenu_page( $parent_slug , $page_title , $menu_title , $capability , $menu_slug , $function );
 } 

/*
 * User Capabilities
 */
 
 http://codex.wordpress.org/Roles_and_Capabilities
 
 // administrator level users lose these abilities in multisite
 // these are now super admin capabilities
 
 update_core
 update_plugins
 update_themes
 install_plugins
 install_themes
 delete_themes
 edit_plugins
 edit_themes
 edit_users
 create_users
 delete_users
 unfiltered_html
 
/*
 * Saving Network Settings
 */
 
 // The register_setting functions work but ONLY on single site settings.
 // Network settings need to be processed and saved.
 
 add_action( ‘admin_init’ ,  ‘process_and_save_my_settings’ );
 
 function process_and_save_my_settings() {
    
    1) Check that your on your network admin page, using $pagenow or $current_screen or other
    2) Check that your form posted information
    3) Set and check a nonce of some kind
    4) Sanitoze the data
    5) save the site_option
    
 }
 
/* 
 * Use Site Option to hide/show things
 */
  
 1) add a network admin menu and provide a setting for the super admin to edit
  
 2) in your "process_and_save_settings" function, save the option
    update_site_option( ‘allow_sites_to_see_stuff’ ,  true );
    
 3) Where you want to show/hide something
 
    if ( get_site_option( ‘allow_sites_to_see_stuff’ ) ) {
        // do stuff
    }
    
/* 
 * Save a site option and use that to update options on every site
 */
 
 /************************ 
    DO NOT USE THIS METHOD 
 *****************************/
 
 update_site_option( ‘awesome_site_option’ ,  $value );

 $blogs = $wpdb->get_results( SELECT blog_id FROM {$wpdb->blogs} … a bunch of other stuff ...

 $value = get_site_option( ‘awesome_site_option’ );

 foreach ( $blogs as $blog ) {
    update_blog_option( $blog['blog_id'] , ‘option_name’ , $value );
 }

    // this way will loop through EVERY blog and kill your site after more than a few blogs
    
 /************************ 
    A Better Way 
 *****************************/
 
 update_site_option( ‘awesome_site_option’ ,  $value );

 add_action( ‘init’ , ‘update_my_site_options’ );

 function update_my_site_options() {
    $value = get_site_option( ‘awesome_site_option’ );
    update_option( ‘awesome_option’ , $value );
 }
    // this is better BUT still happens EVERY page load
    
 /************************ 
    A Still Better Way 
 *****************************/    
 
 // As you save your site option, set a time as well
 update_site_option( ‘awesome_site_option’ , $value );
 update_site_option( ‘awesome_site_option_updated’ , time() );

 // add an action to init hook so it is run when each site loads next
 add_action( ‘init’ , ‘update_my_site_options’ );

 function update_my_site_options() {
    
    // check both time options
    $net_time = get_site_option( ‘awesome_site_option_updated’ );
    $site_time 	= get_option( ‘awesome_option_updated’ );
    
    // compare both times and only do stuff if network option was updated
    if ( $net_time > $site_time ) {
        $value = get_site_option( ‘awesome_site_option’ );
        
        // make sure we save the option and a time for the local option as well
        update_option( ‘awesome_option’ , $value );
        update_option( ‘awesome_option_updated’ , time() );
    }
 } 
 
    // better for doing lots of stuff. If you are doing all this to update just one option, there is still a better way.
    
/*
 * Best way for updating just one option
 */

 // use pre_option_ filter to redifine options based on the network wide setting
 
 add_filter( ‘pre_option_posts_per_page’ , ‘network_limit_posts’ );

 function network_limit_posts( $num_posts ) {
    
    // if the network setting is there, use that
    if ( $network_posts = get_site_option( ‘network_post_limit’ ) ) {
        return $network_posts;
    
    // if not, use the setting as it was
    } else {
        return $num_posts;
    }
 }