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@wpmark https://highrise.digital A Deep Understanding of WordPress Actions and Filters Mark Wilkinson (@wpmark) WordCamp Edinburgh July 2017

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@wpmark https://highrise.digital Mark Wilkinson Using & building WordPress sites for over 10 years as a WordPress developer Owner of Highrise Digital Follow me: @wpmark

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@wpmark https://highrise.digital What are actions/filters? How do they work? Examples Making your code extensible

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@wpmark https://highrise.digital What are actions/filters? How do they work? Examples Making your code extensible

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@wpmark https://highrise.digital What are actions/filters? How do they work? Examples Making your code extensible

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@wpmark https://highrise.digital What are actions/filters? How do they work? Examples Making your code extensible

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@wpmark https://highrise.digital Simply put, hooks are what give us the ability to customize, extend, and enhance WordPress through an API in our themes, plugins, and other custom development efforts. Tom McFarlin, 2012 https://code.tutsplus.com/articles/the-beginners-guide-to-wordpress-actions-and-filters--wp-27373

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@wpmark https://highrise.digital Simply put, hooks are named events, run in the WordPress code that allow us (developers) to run our own code at these points in time. Mark Wilkinson, 2017

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@wpmark https://highrise.digital WordPress Page Life Cycle • Inspects the URL • Queries DB for that content • Queries DB for related data (taxonomies, images etc.) • Loads correct template file • Outputs the content within the theme template

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@wpmark https://highrise.digital @Rarst https://www.rarst.net/ wordpress/wordpress-core- load/

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@wpmark https://highrise.digital How do they work?

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@wpmark https://highrise.digital They are a bit like a shopping list

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@wpmark https://highrise.digital Shopping List Bread Milk Cereal Biscuits

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@wpmark https://highrise.digital Shopping List Bread Milk Cereal Biscuits Beer

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@wpmark https://highrise.digital Shopping List Bread Milk Cereal Biscuits Beer Wine

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@wpmark https://highrise.digital Shopping List Bread Milk Biscuits Wine

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@wpmark https://highrise.digital Hooks Actions & Filters

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@wpmark https://highrise.digital Hooks Actions & Filters

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@wpmark https://highrise.digital do_action(); add_action(); remove_action();

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@wpmark https://highrise.digital do_action( 'action_name', $args );

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@wpmark https://highrise.digital add_action( 'action_name', $function, $priority, $accepted_args );

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@wpmark https://highrise.digital Action Example

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@wpmark https://highrise.digital save_post(); save_post_{$post_type};

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@wpmark https://highrise.digital /wp-includes/post.php do_action( 'save_post', $post_ID, $post, $update );

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@wpmark https://highrise.digital /wp-includes/post.php do_action( 'save_post', $post_ID, $post, $update ); function wpmark_on_save_post( $post_ID, $post, $update ) { update_post_meta( $post_ID, ‘meta_key’, ‘meta_value’ ); } add_action( ‘save_post', ‘wpmark_on_post_save’, 10, 3 );

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@wpmark https://highrise.digital /wp-includes/post.php do_action( 'save_post', $post_ID, $post, $update ); function wpmark_on_save_post( $post_ID, $post, $update ) { update_post_meta( $post_ID, ‘meta_key’, ‘meta_value’ ); } add_action( ‘save_post', ‘wpmark_on_post_save’, 10, 3 ); do_action( ‘save_post_product’, $post_ID, $post, $update );

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@wpmark https://highrise.digital Hooks Actions & Filters

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@wpmark https://highrise.digital apply_filters(); add_filter(); remove_filter();

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@wpmark https://highrise.digital apply_filters( 'filter_name', 'filterable_thing', $args );

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@wpmark https://highrise.digital add_filter( 'filter_name', $function, $priority, $accepted_args );

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@wpmark https://highrise.digital Filter Example

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@wpmark https://highrise.digital

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@wpmark https://highrise.digital /wp-admin/edit-form-advanced.php apply_filters( 'enter_title_here', __( 'Enter title here' ), $post );

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@wpmark https://highrise.digital function wpmark_title_here( $title, $post ) { if ( 'post' === get_post_type( $post ) ) { $title = __( 'Article Title' ); } return $title; } add_action( 'enter_title_here', ‘wpmark_title_here’,10, 2 ); apply_filters( 'enter_title_here', __( 'Enter title here' ), $post ); /wp-admin/edit-form-advanced.php

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@wpmark https://highrise.digital function wpmark_title_here( $title, $post ) { if ( 'post' === get_post_type( $post ) ) { $title = __( 'Article Title' ); } return $title; } add_action( 'enter_title_here', ‘wpmark_title_here’, 10, 2 ); apply_filters( 'enter_title_here', __( 'Enter title here' ), $post ); /wp-admin/edit-form-advanced.php

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@wpmark https://highrise.digital Making your own code extensible

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@wpmark https://highrise.digital Setting up arrays $job_posts = new WP_Query( array( ‘post_type’ => ‘wpmark_job’, ‘posts_per_page => 12 ) );

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@wpmark https://highrise.digital Setting up arrays $job_posts = new WP_Query( apply_filters( ‘wpmark_job_post_query_args’, array( ‘post_type’ => ‘wpmark_job’, ‘posts_per_page => 12 ) ) );

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@wpmark https://highrise.digital In Loops while ( $job_posts->have_posts() ) : $job_posts->the_post(); do_action( ‘wpmark_job_post’, $post ); endwhile;

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@wpmark https://highrise.digital Function returns function wpmark_sub_title( $post_id = 0 ) { return get_post_meta( $post_id, ‘subtitle’, true ); }

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@wpmark https://highrise.digital Function returns function wpmark_sub_title( $post_id = 0 ) { return apply_filters( ‘wpmark_sub_title’, get_post_meta( $post_id, ‘subtitle, true ), $post_id ); }

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@wpmark https://highrise.digital Recap

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@wpmark https://highrise.digital do_action(); apply_filters();

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@wpmark https://highrise.digital add_action(); add_filter();

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@wpmark https://highrise.digital Remember Filters - always return the ‘filterable thing’!

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@wpmark https://highrise.digital Try to make your own code extensible Using do_action() & apply_filters()

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@wpmark https://highrise.digital Thank you for listening Questions? @wpmark