The Secret to Mastering WordPress Multi-site 

Hello! Juliette Reinders Folmer @jrf_nl @jrfnl @jrf 

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UI for multi-network setup: https://wordpress.org/plugins/wp-multi-network/ 

How Does It Work ? xhowardlee 

File System 1 WP installation 1 plugins folder 1 themes folder 1 must-use plugins folder 1 translations folder 1 uploads folder 1 WP installation 1 plugins folder 1 themes folder 1 must-use plugins folder 1 translations folder 1 uploads folder with #n subfolders in a sites subdirectory 

Database 1 database no network tables 1 options table 1 set of user tables 1 set of content tables 1 database 1 set of network tables #n sets of options tables 1 set of user tables #n sets of content tables 

Database wp_comments wp_commentmeta wp_links wp_options wp_posts wp_postmeta wp_terms wp_termmeta wp_term_relationships wp_term_taxonomy wp_users wp_usermeta wp_users wp_usermeta wp_comments wp_commentmeta wp_links wp_options wp_posts wp_postmeta wp_terms wp_termmeta wp_term_relationships wp_term_taxonomy wp_2_comments wp_2_commentmeta wp_2_links wp_2_options wp_2_posts wp_2_postmeta wp_2_terms wp_2_termmeta wp_2_term_relationships wp_2_term_taxonomy wp_3_comments wp_3_commentmeta wp_3_links wp_3_options wp_3_posts wp_3_postmeta wp_3_terms wp_3_termmeta wp_3_term_relationships wp_3_term_taxonomy wp_blogs wp_blog_versions wp_registration_log wp_signups wp_site wp_sitemeta 

Users 1 set of users 1 set of user meta per user 1 set of user capabilities Highest role: admin 1 set of users 1 set of user meta per user 1 set of user capabilities per sub-site Highest role: super-admin 

Plugin Actions ▪ Activate ▪ Deactivate ▪ Uninstall ▪ Network Activate ▪ Activate ▪ Network Deactivate ▪ Deactivate ▪ Uninstall 

What is needed for a plugin or theme to be compatible with WordPress multi-site ? 

NOTHING (for most plugins and nearly all themes) 

Fine Tuning for the Other 20% djouby 

 Database  Autoloaded Options  Plugins  Theme  Rewrite Rules  $GLOBALS       Understanding Context 

 Database  Autoloaded Options  Plugins  Theme  Rewrite Rules  $GLOBALS             Understanding Context 

 Database  Autoloaded Options  Plugins  Theme  Rewrite Rules  $GLOBALS             Understanding Context 

 Database  Autoloaded Options  Plugins  Theme  Rewrite Rules  $GLOBALS             Understanding Context 

Switching Between Blogs switch_to_blog() restore_current_blog() ms_is_switched() 

 Database  Autoloaded Options  Plugins  Theme  Rewrite Rules  $GLOBALS                /  / Understanding Context 

Uh oh.... 

Terminology Network of Networks •get_network_by_path() Network • get_site_by_path() • WP_Network • $current_site • is_main_network() • get_current_site() • is_network_admin() • is_super_admin() Site • WP_Site • $current_blog • is_main_site() • get_blog_details() • get_site() • get_sites() • is_admin() • current_user_can() 

Confused yet ? 

“ People will write code 

Become a Better Developer 

Network Plugins

Network Plugins

Non-Network Plugins

Update, don't Activate class Prefix_My_Class { const VERSION = '1.0'; function __construct() { $option = get_option( 'prefix_option' ); if ( false === $option || ! isset( $option['version'] ) || version_compare( $option['version'], self::VERSION, '<') ) { $this->upgrade( $option ); } } } 

Update, don't Activate class Prefix_My_Class { const VERSION = '1.0'; protected function upgrade( $option ) { // Add DB tables // Add action to flush rewrite rules at a later hook // Add cron jobs // etc $option['version'] = self::VERSION; update_option( 'prefix_option', $option ) } } 

Deactivation & Uninstall Routines jackiebabe 

Dealing with User Data  Differentiate between global and local data  "Blog" specific meta keys  is_super_admin() greyerbaby 

Rewrite Rules Jeff Djevdet flush_rewrite_rules() 

Scheduling Cron Events  Differentiate between global and local data  is_main_site() irkengirdib 

is_multisite() 

is_network_admin() Action: 'network_admin_menu' wp_is_large_network () current_user_can _for_blog() self_admin_url() get_current_blog_id () Other Useful Snippets 

Thanks! Any questions ? Slides: https://speakerdeck.com/jrf @jrf_nl @jrfnl @jrf