There's A HOOK for that

James Bonham

Team lead @

James Bonham

Organiser @

– CODEX

A hook is an event... invoked by do_action() or apply_filters()

– less geeky person

A hook GIVES YOU THE MEANS TO Do something ELSE OR MODIFY existing stuff

action HOOK

DO SOMETHING WHEN A specific event take place in WordPress, such as publishing a post

Do Something

action HOOK

add_action() hooks a function onto the specified hook.

 

do_action() executes all THE hooked functions for a given hook, at the right moment.

Do Something

Action HOOK: Concept

 

When the sun shines, COOL DOWN THE OFFICE and close some blinds

Action HOOK: Concept

 

sunshine = Event where we need a hook

cool_down_office = Action to add to hook 

close_blinds = Action to add to hook

 

Action HOOK: Concept

 

Make it sunny

COOL IT DOWN

MAKE IT HAPPEN

function sunshine() {
    remove_clouds();
    do_action( 'sunny' );
}
function cool_down_office() {
   $temp = get_aircon_temp();
   if ( $temp > 21 ) {
      set_aircon_temp( 18 );
   }
}
add_action( 'sunny', 'cool_down_office', 1 );

Action HOOK: Concept

 

Close blinds

MAKE IT HAPPEN

function close_blinds() {
    $blinds = get_blinds('roof');
    foreach ( $blinds as $blind ) {
        close_blind( $blind );
    }
}
add_action( 'sunny', 'close_blinds', 2 );

PAGE EXCERPTS

DO SOMETHING

/**
 * Add excerpts to pages.
 */
function xyz_support_page_excerpts() {
	add_post_type_support( 'page', 'excerpt' );
}
add_action( 'init', 'xyz_support_page_excerpts' );

Search ALL

DO SOMETHING

/**
 * Override post types search should include.
 *
 * $query object The query to be run.
 */
function xyz_search_more( $query ) {
  if ( ! is_admin() && $query->is_main_query() ) {
    if ( $query->is_search ) {
      $query->set( 'post_type', ['post', 'page', 'movie'] );
    }
  }
}
add_action( 'pre_get_posts', 'xyz_search_more' );

NOTIFY

DO SOMETHING

/**
 * Email me when someone publishes.
 */
function xyz_email_me( $id, $post ) {
   wp_mail( 'jb@peytz.dk', "Blog updated", ...
      ...'Hey, new Content! ' . get_permalink( $id ) );
}
add_action( 'publish_post', 'xyz_email_me' );

option revisions

DO SOMETHING

/**
 * Updates the log
 *
 * @param string $option Name of the option that has been updated
 * @param string $old_value The old value before the user changed it
 * @param string $new_value The new value that the user changed it to
 * @since 1.0.0
 */
function log_option_change( $option, $old_value, $value ) {

  if( $old_value == $value || $option == 'option_logger' ) {
    return;
  }

  if( substr( $option, 0, 1 ) == '_' ) {
    return;
  }

  ...
 ...

  // Fetch the existing log or sets a blank array if not found
  $log = get_option( 'option_logger', array() );

  // Build the new entry for the log
  $current_user = wp_get_current_user();
  $new_item = array(
    'option'    => $option,
    'old_value' => $old_value,
    'value'     => $value,
    'user_id'   => $current_user->ID,
    'time'      => current_time( 'timestamp' )
  );
 
  // Append the item to the top of the log
  array_unshift( $log, $new_item );

  // Remove the last item if the log is getting too long
  if( count( $log ) > 200 ) {
    array_pop( $log );
  }

  // Update the log, now it's been modified with the new entry
  update_option( 'option_logger', $log );
}
add_action( 'updated_option', 'option_logger', 10, 3 );
add_action ( string $tag, callback $function_to_add, 
  int $priority = 10, int $accepted_args = 1 )
do_action ( string $tag, mixed $arg = '' )

ACTION REFERENCE

DO SOMETHING

https://developer.wordpress.org/reference/functions/add_action/
https://developer.wordpress.org/reference/functions/do_action/

PRiority

DO SOMETHING

do_action( 'hook' )
add_action(,,3)
add_action(,,2)
add_action(,,9)
add_action(,,1)

priority

DO SOMETHING

do_action( 'hook' )
add_action(,,1)
add_action(,,2)
add_action(,,3)
add_action(,,9)

Filters sit between the database and the browser

FILTER HOOK

MODIFY Something

add_FILTER() hooks a function onto the specified FILTER hook.

 

Apply_Filters() executes all THE hooked functions, returning modified content.

FILTER HOOK

MODIFY Something

When someone speaks, they should shout "Listen to me!" first, And then shout what they planned to say..

FILTER HOOK: Concept


FILTER HOOK: Concept

 

speak = Event when person speaks

content = What the person is saying

prepend_to_content = Filter to prepend 'Listen to me!' 

shout_message = Filter to make text uppercase

 

FILTER HOOK: Concept

 

SAY IT

PREPEND "LISTEN..."

function speak( $content ) {
    echo apply_filters( 'the_speech', $content );
}
function listen_to_me( $content ) {
   return 'Listen to me! ' . $content;
}
add_filter( 'the_speech', 'listen_to_me', 1 );
function shout_message( $content ) {
   return strtoupper( $content );
}
add_filter( 'the_speech', 'shout_message', 2 );

Make uc

READ MORE

function xyz_excerpt_more( $more ) {
    return '…';
}
add_filter( 'excerpt_more', 'xyz_excerpt_more' );

MODIFY Something

READ MORE

MODIFY Something

ADD BODY CLASS

MODIFY Something

function xyz_add_body_class( $classes ) {
    $classes[] = 'site-' . sanitize_title( get_bloginfo( 'name' ) );

    return $classes;
}
add_filter( 'body_class', 'xyz_add_body_class' );

SHOW EXCERPTS

MODIFY Something

/**
 * Always show excerpt field.
 * $hidden array An array of meta boxes hidden by default.
 * $screen object WP_Screen object of the current screen.
 */
function xyz_show_excerpt( $hidden, $screen ) {
	if ( 'post' == $screen->base ) {
		$key = array_search( 'postexcerpt', $hidden );
		if( !empty( $key ) ) {
			unset( $hidden[ $key ] );
			$hidden = array_values( $hidden );
		}
	}

	return $hidden;
}
add_filter( 'default_hidden_meta_boxes', 'xyz_show_excerpt', 10, 2 );

FILTER REFERENCE

MODIFY Something

add_filter ( string $tag, callback $function_to_add,
  int $priority = 10, int $accepted_args = 1 )
apply_filters ( string $tag, mixed $value )
https://developer.wordpress.org/reference/functions/add_filter/
https://developer.wordpress.org/reference/functions/apply_filters/

imagine a cms without hooks

imagine a cms without hooks

DON't BE AFRAID

open plugins and see how they work

just go write a plugin!

child themes...

...are not always the answer!

try A LITTLE PLUGIN WITH a hook

You want something different?

There's a hook for that!

@jamesbonham

There's a Hook For That

By James Bonham

There's a Hook For That

My presentation from WordCamp Denmark 2015. See the presentation here... http://wordpress.tv/2015/12/07/james-bonham-theres-a-hook-for-that/

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