The publish_post hook is one I’ve seen a lot in tutorials and such. Even has its own page in the codex.
But surprise! That hook doesn’t actually exist, at least not if you search for do_action\(\s?.publish_post.
When I was learning to dig into core, this baffled me. What was this publish_post sorcery? Why wouldn’t it work on my custom post types???
Here’s a secret: The actual hook in core looks like this "{$new_status}_{$post->post_type}". It’s part of a small function in wp-includes/post.php (line 3321 at the time of writing), and there’s another equally useful variable hook right before it.
function wp_transition_post_status($new_status, $old_status, $post) {
do_action('transition_post_status', $new_status, $old_status, $post);
do_action("{$old_status}_to_{$new_status}", $post);
do_action("{$new_status}_{$post->post_type}", $post->ID, $post);
}
There are quite a few of these variable hooks in core, I encourage you to go look at them, here’s a list I scraped together:
Actions
"add_option_{$option}"
"add_site_option_{$option}"
"add_{$meta_type}_meta"
"added_{$meta_type}_meta"
"admin_head-$hook_suffix"
"admin_head-$hook_suffix");
"admin_head_{$content_func}"
"admin_print_scripts-$hook_suffix"
"admin_print_scripts-$hook_suffix");
"admin_print_styles-$hook_suffix"
"admin_print_styles-$hook_suffix");
"after-{$taxonomy}-table"
"after_plugin_row_$plugin_file"
"after_theme_row_$stylesheet"
"comment_{$new_status}_{$comment->comment_type}"
"comment_{$old_status}_to_{$new_status}"
"create_$taxonomy"
"created_$taxonomy"
"delete_$taxonomy"
"delete_option_$option"
"delete_site_option_{$option}"
"delete_{$meta_type}_meta"
"delete_{$meta_type}meta"
"deleted_{$meta_type}_meta"
"deleted_{$meta_type}meta"
"edit_$taxonomy"
"edited_$taxonomy"
"get_template_part_{$slug}"
"in_plugin_update_message-{$file}"
"in_theme_update_message-{$theme_key}"
"install_plugins_$tab"
"install_plugins_pre_$tab"
"install_themes_pre_{$tab}"
"install_themes_{$tab}"
"manage_{$post->post_type}_posts_custom_column"
"media_upload_$tab");
"media_upload_$type");
"save_post_{$post->post_type}"
"update-custom_{$action}"
"update_option_{$option}"
"update_site_option_{$option}"
"update_{$meta_type}_meta"
"updated_{$meta_type}_meta"
"{$new_status}_{$post->post_type}"
"{$old_status}_to_{$new_status}"
"{$taxonomy}_add_form"
"{$taxonomy}_add_form_fields"
"{$taxonomy}_pre_add_form"
"{$taxonomy}_pre_edit_form"
"{$taxonomy}_term_new_form_tag"
Filters
"_wp_post_revision_field_$field"
"add_{$meta_type}_metadata"
"async_upload_{$type}"
"auth_post_meta_{$meta_key}"
"blog_option_{$option}"
"bulk_actions-{$this->screen->id}"
"comment_form_field_{$name}"
"current_theme_supports-{$feature}"
"customize_sanitize_js_{$this->id}"
"customize_sanitize_{$this->id}"
"delete_{$meta_type}_metadata"
"edit_$field"
"edit_post_{$field}"
"edit_term_{$field}"
"edit_user_{$field}"
"edit_{$field}"
"edit_{$taxonomy}_{$field}"
"extra_{$context}_headers"
"get_$taxonomy"
"get_the_generator_{$type}"
"get_user_option_{$option}"
"get_{$adjacent}_post_join"
"get_{$adjacent}_post_sort"
"get_{$adjacent}_post_where"
"get_{$meta_type}_metadata"
"install_plugins_table_api_args_$tab"
"manage_taxonomies_for_{$post_type}_columns"
"manage_{$post_type}_posts_columns"
"manage_{$this->screen->id}_sortable_columns"
"manage_{$this->screen->taxonomy}_custom_column"
"nav_menu_items_{$post_type_name}"
"option_page_capability_{$option_page}"
"post_type_labels_{$post_type}"
"post_{$field}"
"postbox_classes_{$page}_{$id}"
"pre_$field"
"pre_post_{$field}"
"pre_term_{$field}"
"pre_user_{$field}"
"pre_{$field}"
"pre_{$taxonomy}_{$field}"
"sanitize_option_{$option}"
"sanitize_{$meta_type}_meta_{$meta_key}"
"shortcode_atts_{$shortcode}"
"term_links-$taxonomy"
"term_{$field}"
"term_{$field}_rss"
"theme_action_links_$stylesheet"
"theme_mod_{$name}"
"update_{$meta_type}_metadata"
"user_{$field}"
"user_{$name}_label"
"views_{$this->screen->id}"
"wp_nav_menu_{$menu->slug}_items"
"{$adjacent}_image_link"
"{$adjacent}_post_link"
"{$adjacent}_post_rel_link"
"{$boundary}_post_rel_link"
"{$field_no_prefix}_edit_pre"
"{$field_no_prefix}_save_pre"
"{$field}_pre"
"{$taxonomy}_row_actions"
"{$taxonomy}_{$field}"
"{$taxonomy}_{$field}_rss"
"{$type}_template"