WordPress Flow

gistfile1.txt

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'

Thanks so much! ★

Thanks, this is excellent! Has this changed any over the past few years?

@MQuigg it's quite out of date, but generally still accurate

Landed from https://twitter.com/wpmark/status/1463817518565445633

Very nice @johnbillion do you think we could continously auto-generate this from source code?

To be honest I don't think so. The intention isn't to cover every action that fires and every file that loads, just the ones that are of interest to plugin and theme developers and contributors. I think that's best done with manual curation.

Something automated that describes the difference in the loading flow from one version to the next would be useful though.

Thanks for sharing. Its really helpful.

I've just been made aware of https://hookorder.com/ by Jānis Elsts which is a more comprehensive and better formatted way of viewing the load order and hooks that fire during a request to WordPress. Check it out!

@johnbillion Very nice! We've been using his Admin Menu Editor Pro plugin for years. Thanks to both of you for this very useful information.

Awesome thanks for the link, it looks very useful!