WordPress Flow

https://gist.github.com/johnbillion/4fa3c4228a8bb53cc71d

WordPress Flow

 

INITIALISATION
==============

load wp-config.php
set up default constants
load wp-content/advanced-cache.php if it exists
load wp-content/db.php if it exists
connect to mysql, select db
load object cache (object-cache.php if it exists, or wp-include/cache.php if not)
load wp-content/sunrise.php if it exists (multisite only)
load l10n library
load mu plugins
DO_ACTION 'muplugins_loaded' (only accessible to mu plugins)
load active plugins
load pluggables.php
DO_ACTION 'plugins_loaded' (first hook available to plugins)
load rewrite rules
instantiate $wp_query, $wp_rewrite and $wp.
	$wp_query is a global instance of the WP_Query class. For more info, see ANY QUERY
	$wp_rewrite is a global instance of the WP_Rewrite class and contains our rewrite rules and functions
	$wp is a global instance of the WP class and contains the functions that will parse our request and perform the main query (see REQUEST)
DO_ACTION 'setup_theme'
include child theme functions.php
include parent theme functions.php
DO_ACTION 'after_setup_theme' (first hook available to themes)
set up current user object
DO_ACTION 'init'
register widgets (DO_ACTION 'widget_init')
call wp() (which calls $wp->main())


REQUEST
=======

$wp->parse_request()
	loop over rewrite rules to find a match
	APPLY_FILTERS 'query_vars' to the publicly available query vars
	fill query vars with $_POSTs, $_GETs, and rewritten vars
	APPLY_FILTERS 'request' to the request variables
	DO_ACTION_REF_ARRAY 'parse_request' with array of request vars (query vars, request, matched rewrite rules, etc)

DO_ACTION_REF_ARRAY 'send_headers' with the 'WP' object.

THE MAIN QUERY
==============

$wp->query_posts()
	goto ANY QUERY

if posts are empty, set is_404() (and send 404 headers)
set all the query_vars to global variables
DO_ACTION_REF_ARRAY 'wp' with the main WP object


	ANY QUERY
	=========

	WP_Query->query( query vars )
		WP_Query->parse_query( query vars )
			build query parameters based off query vars
			set WP_Query->is_* vars based off query parameters
				if this query is $wp_the_query then these determine the values of the global is_*() functions too
			DO_ACTION_REF_ARRAY 'parse_query' with WP_Query object (query parameters, query vars, conditionals)
		WP_Query->get_posts()
			DO_ACTION_REF_ARRAY 'pre_get_posts' with WP_Query object
			APPLY_FILTERS_REF_ARRAY 'posts_search' with search SQL
			series of APPLY_FILTERS on the query SQL (if suppress_filters=false):
			 * posts_where
			 * posts_join
			 * posts_where_paged
			 * posts_groupby
			 * posts_join_paged
			 * posts_orderby
			 * posts_distinct
			 * post_limits
			 * posts_fields
			 * posts_clauses
			APPLY_FILTERS_REF_ARRAY 'posts_request' (if suppress_filters=false)
			fetch posts from the database
			APPLY_FILTERS_REF_ARRAY 'posts_results' (if suppress_filters=false)
			prepend sticky posts
			APPLY_FILTERS_REF_ARRAY 'the_posts' (if suppress_filters=false)
			return posts

TEMPLATE
========

DO_ACTION 'template_redirect'
if is_feed()
	load the feed template
else
	look for template file in theme based on template hierarchy
	APPLY_FILTERS 'template_include'
	load the template file (which usually runs a loop @TODO document a loop)
DO_ACTION 'shutdown'