Download to read offline
Uploaded byDrewAPicture
There's a Filter For That
This document discusses WordPress filters and provides examples of how they can be used. It begins by defining a filter as a function that takes a WordPress value, optionally modifies it, and returns the resulting value. It then explains the apply_filters() function and lists over 1,300 filter hooks in core. Examples are given for using filters to modify content in the editor, customize admin menu ordering, filter meta boxes and post types when deleting users. Front-end filters discussed include modifying post content, body classes, and excerpt length. The document concludes with filters useful for development like modifying plugins/themes listings and enabling post by email.
More Related Content
Similar to There's a Filter For That
There's a Filter For That
- 1. drewf.us/wcabq13 THERE’S A FILTERFORTHAT Drew Jaynes | WCABQ ’13
- 2. drewf.us/wcabq13 WHO I AM DrewJaynes Web Engineer, 10up Core Contributor WordPress Docs Team
- 3. drewf.us/wcabq13 WHAT IS AFILTER? A filter is a function that: 1.Takes a specific WordPress value 2. (maybe) modifies it 3. Spits the resulting value back out
- 4.
- 5.
- 6. drewf.us/wcabq13 apply_filters() – 1,300+ filterhooks in core (3.6+) – Filter values of all types, modify default behavior – Multiple filters run per hook, based on priority
- 7. drewf.us/wcabq13 ADDING OR REMOVINGFILTERS add_filter( 'hook_name', 'callback', #priority, #args ); – When removing a filter, the hook, callback and priority must match exactly. Fails silently. remove_filter( 'hook_name', 'callback', #priority ); – Define priority any time. Define the args count + 1 if additional args are passed from the filter hook
- 8. drewf.us/wcabq13 ALLTOGETHER NOW // $valueis filterable apply_filters( ‘hook_name’, $value, (optional) $args ); function callback( $value, $arg ) { // do stuff return $value; } add_filter( 'hook_name', 'callback', 10, 2 );
- 9.
- 10. drewf.us/wcabq13 ‘enter_title_here’ Args:(string $enter_title_here, WP_Post$post) – Match title prompt text to your custom post type – Adds polish to the experience Filter ‘Enter title here’ placeholder text
- 11. drewf.us/wcabq13 ‘post_updated_messages’ Args:(array $messages) – Nothandled by WordPress out of the box – Use with custom post types – Customize ‘Post updated’,‘Post deleted’, etc. Filter post updated|published|trashed|etc. messages.
- 12. drewf.us/wcabq13 ‘admin_post_thumbnail_html’ Args:(string $content, int$post->ID) ‘media_view_strings’ Args:(array $strings, WP_Post $post) Filter HTML output of Featured Image meta box Filter media strings localized for JavaScript
- 13.
- 14. drewf.us/wcabq13 ‘the_editor_content’ Args:(string $content) – Pre-fabpost template – Check if the content is empty Filter the content in the editor (new and existing posts)
- 15. drewf.us/wcabq13 ‘custom_menu_order’ Args:(bool false) Enable/disable customadmin menu ordering ‘menu_order’ Args:(array $menu_order) Filter the top-level menu order in the admin menu
- 16. drewf.us/wcabq13 ‘custom_menu_order’ // enable custommenu order add_filter( ‘custom_menu_order’, __return_true’ );
- 17. drewf.us/wcabq13 ‘menu_order’ function change_menu_order( $menu_order); return array( 'index.php', 'separator1', 'edit.php', 'edit.php?post_type=page', 'users.php', 'upload.php', 'edit-comments.php', 'separator2', 'themes.php', 'plugins.php', 'tools.php', 'options-general.php', 'separator-last' ); } add_filter( ‘menu_order’, ‘change_menu_order’ );
- 18. drewf.us/wcabq13 ‘default_hidden_meta_boxes’ Args:(array $hidden, WP_Screen$screen) – Standardize UX for all users – Doesn’t prevent future user changes Contextually filter meta boxes hidden by default
- 19. drewf.us/wcabq13 ‘post_types_to_delete_with_user’ Args:(array $post_types_to_delete, int$id) – Overrides ‘delete_with_user’ post type setting Filter which post types to delete with a user
- 20.
- 21. drewf.us/wcabq13 ‘the_content’ (string $content) – Frequentlyused and abused in themes and plugins – Litmus test: is it content? Filter the post content
- 22. drewf.us/wcabq13 ‘post|body_class’ Args:(array $classes) – Relianton themes using post|body_class() in templates – Style things in specific contexts, e.g. post_type, post format, etc. Filter body classes or post classes
- 23. drewf.us/wcabq13 ‘excerpt_length’ Args:(int $number) – Commonlyfiltered by themes, default is 55 characters Filter the length (in characters) of the excerpt
- 24. drewf.us/wcabq13 ‘show_admin_bar’ (bool true) // DisableToolbar add_filter( ‘show_admin_bar’, ‘__return_false’ ); Show/hide theToolbar on the front-end
- 25. drewf.us/wcabq13 ‘disable_captions’ (bool false) // Disablecaptions add_filter( ‘disable_captions’, ‘__return_true’ ); Disable/enable image captions
- 26.
- 27. drewf.us/wcabq13 ‘plugins|themes_api_*’ – Different resultobject, arguments, or complete overhaul Filter plugin or theme installer pages ‘plugins|themes_api_args’ ‘plugins|themes_api’ ‘plugins|themes_api_result’
- 28. drewf.us/wcabq13 ‘enable_post_by_email_configuration’ Args:(bool false) // disablepost by email add_filter( ‘enable_post_by_email_configuration’, ‘__return_false’ ); Enable/disable Post by Email
- 29. drewf.us/wcabq13 MOAR DEV FILTERS ‘request’ Args:(array$query_vars) Directly filter the current request’s query vars ‘shortcode_atts_$shortcode’ Args:(array $out, array $pairs, array $atts) Filter a shortcode’s default attributes (3.6+) – Output atts, default atts, user-defined atts
- 30. drewf.us/wcabq13 MOAR DEV FILTERS ‘wp_xmlrpc_server_class’ Args:(string$class) Filter the class used for handling XML-RPC requests ‘xmlrpc_methods’ Args:(array $methods) Register custom XML-RPC methods
- 31.