5 Ws of Hookin

5 W's of Hookin'

Nowell VanHoesen@NowellVanHoesen

about.me/NowellVanHoesen

Hookin' Overview

What are Hooks

Who hooks

Why hook

Where are they

When to hook

Examples

@NowellVanHoesen5 W's of Hookin'

What are hooks?

A specific place/time in WordPress code execution to add functionality or change data.


What are hooks?


Types:

– Action: add functionality at a specific point when an event happens or is about to happen.


What are hooks?


Types:

– Action: add functionality at a specific point when an event happens or is about to happen.

– Filter: modify data before some event( save, display )


Who hooks?


Who hooks?

Any one who wants to add custom code to change how WordPress behaves or modify what is output to the browser.


Who hooks?

Any one who wants to add custom code to change how WordPress behaves or modify what is output to the browser.

Anyone who wants to allow others to build on to their plugin or theme.


Why


Why

use hooks


Why

use hooks● Tweak

functionality/output to better fit your needs


Why

use hooks● Tweak


● Maintain your customizations when updating


Why

use hooks● Tweak



create hooks


Why

use hooks● Tweak



create hooks● Allow others to add

functionality


Why

use hooks● Tweak



create hooks● Allow others to add

functionality

● Allow others to filter output from your plugin/theme


Where...

can I find them


Where...

can I find them● WordPress core


Where...


● Themes


Where...


● Themes

● Plugins


Where...


● Themes

● Plugins

can I create them


Where...


● Themes

● Plugins

can I create them● Themes


Where...


● Themes

● Plugins


● Plugins


Where...


● Themes

● Plugins


● Plugins

● WordPress core


How?

Actions Filters


How?

Actions● add_action( t, f, p, a )

Filters● add_filter( t, f, p, a )


t = tag f = function p = priority a = # args

How?


● remove_action( t, f, p, a )


● remove_filter( t, f, p, a )



How?



● do_action( t, f, p, a )



● apply_filters( t, f, p, a )



How?



● do_action( t, f, p, a )



● apply_filters( t, f, p, a )


http://codex.wordpress.org/Plugin_APIt = tag f = function p = priority a = # args

Action hook example 1// wp_enqueue_scripts actionadd_action( 'wp_enqueue_scripts', 'nv_added_styles' );

function nv_added_styles() { if ( !is_admin() ) { wp_register_style( 'nv-ie-fix', get_bloginfo( 'stylesheet_directory' ) . '/ie.css', false ); $GLOBALS['wp_styles']->add_data( 'nv-ie-fix', 'conditional', 'lte IE 8' ); wp_enqueue_style( 'nv-ie-fix' ); }}


Action hook example 2add_action( 'pre_get_posts', 'my_get_posts' );function my_get_posts( $query ) { global $wp_the_query; if( $wp_the_query === $query && $query->is_home() ) { add_filter( 'posts_where' , 'posts_where' ); $category_id = get_cat_ID( 'Scribblings' ); $query->set( 'cat', $category_id ); } else if ( is_archive() && is_date() && !is_category()) { if ( !isset( $query->query_vars['post_type'] ) ) { $query->set( 'post_type', array( 'post', 'myoldhouse', 'snapshots' ) ); $query->set( 'posts_per_page', -1 ); } }}function posts_where( $where ) { $where = " AND ( ( wp_term_relationships.term_taxonomy_id IN (1) AND wp_posts.post_type = 'post' ) OR ( wp_posts.post_type IN ('myoldhouse', 'snapshots') ) ) AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private')"; return $where;}


Filter hook examplesadd_filter( 'the_title', 'nv_the_title', 10, 2 );

function nv_the_title( $title, $id ) { if ( !is_admin() ) { $title = 'WCCbus - ' . $title; } return $title;}

// what core runsreturn apply_filters( 'the_title', $title, $id );

add_filter( 'enter_title_here', 'change_default_post_title', 10, 2 );

function change_default_post_title( $text, $post ) { if ( 'post' == get_post_type( $post ) ) { return $text . “ - Required”; }}


Time to go live...


Resources


Plugin API on the codex

- http://codex.wordpress.org/Plugin_API

Drew Jaynes – Filter of the Day: Three filters a day for 365 days

- http://fotd.werdswords.com/

http://codex.wordpress.org/Plugin_API

http://fotd.werdswords.com/

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