Getting to know all WordPress functions

Functions on WordPress

On WordPress, the functions are placed in the functions.php file, and you can change the functions in this file or put custom code in it.

The functions.php file is automatically loaded when you install and activate a WordPress theme, and we've included all the functions here.

This file acts like a WordPress plugin for your WordPress site and is automatically activated with your current theme. The functions.php file uses PHP code to add features or change default features on the site.

For example, a WordPress theme might add a bit of code to the functions.php file to add a new widget area to the footer, or add a custom welcome message to the WordPress dashboard.

Editing the functions.php file with custom code allows you to add post types, categories, short codes, and more to improve your website.

In any case, with the help of this file, you can add endless features to the website without installing a plugin.

Where is the location of the WordPress functions file?

The location of the functions.php file is in the template folder. If you want to add a piece of code to a WordPress site, adding it to the functions.php file is one option. But this is usually not the best way to do it. WordPress tries to separate design and functionality as much as possible. That's why we have themes that define design and plugins that define functionality.

It's even better if you can change your WordPress theme without changing how your site works, or change your plugins without affecting your site design.

If you decide to edit this file, please be very careful or preferably get help from an expert. In the following, we have given 3 important reasons to be careful when editing the functions.php file.

3 important reasons to be cautious when editing the functions.php file

Editing this file should be done carefully. 3 reasons for the importance of this issue are:

Editing functions on WordPress will be lost when the theme is updated.
If you change your WordPress theme, the edits will be lost.
Creating coding errors in the functions file can damage the site.

Even something as simple as an extra semicolon can cause your entire site to fail. So if you need to change this file, get help from experienced people.

Coding mistakes in the functions.php file can also lead to various WordPress errors. You only need to edit a functions.php file if you have a child theme, and code snippets are only used with the active child theme. For example, you might want to add snippets for custom fonts, style sheets, or a language translation file specifically for a theme.

Introduction of all WordPress functions

WordPress files define many useful PHP functions. Some functions on WordPress, known as template tags, are specifically defined for use in WordPress themes. There are also some functions related to actions and filters (Plugin API), which are mainly used for developing plugins. The rest is used to create the core functionality of WordPress.

Many core WordPress functions are useful for plugin and theme developers. So, here we list most of the main functions, excluding the template tags.

All these functions are basic and necessary, and knowing them is essential for people who want to make changes to your WordPress codes.

Post functions

get_adjacent_post
get_boundary_post
get_children
get_extended
get_next_post
get_next_posts_link
next_posts_link
get_permalink
the_permalink
get_the_excerpt
the_excerpt
get_the_post_thumbnail
get_post
get_post_field
get_post_ancestors
get_post_mime_type
get_post_status
get_post_format
set_post_format
get_edit_post_link
get_delete_post_link
get_previous_post
get_previous_posts_link
previous_posts_link
get_posts
have_posts
is_post
is_single
is_sticky
get_the_ID
the_ID
the_post
wp_get_recent_posts
wp_get_single_post
has_post_thumbnail
has_excerpt
has_post_format

Custom post functions

register_post_status

Custom post type

register_post_type
is_post_type_archive
post_type_archive_title
add_post_type_support
remove_post_type_support
post_type_supports
set_post_type
post_type_exists
get_post_type
get_post_types
get_post_type_archive_link
get_post_type_object
get_post_type_capabilities
get_post_type_labels
is_post_type_hierarchical

Post insertion and deletion

wp_delete_post
wp_insert_post
wp_publish_post
wp_trash_post
wp_update_post

Custom fields (postmeta)

add_post_meta
delete_post_meta
get_post_custom
get_post_custom_keys
get_post_custom_values
get_post_meta
update_post_meta
register_meta

attachments

get_attached_file
image_resize
image_edit_before_change
is_attachment
is_local_attachment
set_post_thumbnail
update_attached_file
wp_attachment_is_image
wp_create_thumbnail
wp_insert_attachment
wp_delete_attachment
wp_get_attachment_image
wp_get_attachment_link
wp_get_attachment_image_src
wp_get_attachment_metadata
wp_get_attachment_thumb_file
wp_get_attachment_thumb_url
wp_get_attachment_url
wp_check_for_changed_slugs
wp_count_posts
wp_get_mime_types
wp_mime_type_icon
wp_generate_attachment_metadata
wp_prepare_attachment_for_js
wp_update_attachment_metadata

Bookmark

get_bookmark
get_bookmarks
wp_list_bookmarks

Main items

wp_get_post_categories
wp_set_post_categories
wp_get_post_tags
wp_set_post_tags
wp_get_post_terms
wp_set_post_terms
wp_count_terms
has_term
is_object_in_term

Other cases

add_meta_box
remove_meta_box
get_the_ID
the_ID
get_the_author
the_author
get_the_author_posts
get_the_content
the_content
get_the_title
the_title
the_title_attribute
wp_trim_excerpt
wp_get_post_revision
wp_get_post_revisions
wp_is_post_revision
paginate_links

Create category

wp_create_category
wp_delete_category
wp_insert_category

Grouping

get_object_taxonomies
get_edit_term_link
get_taxonomy
get_taxonomies
get_term
get_the_term_list
get_term_by
the_terms
get_the_terms
get_term_children
get_term_link
get_terms
is_taxonomy
is_tax
is_taxonomy_hierarchical
is_term
taxonomy_exists
term_exists
register_taxonomy
register_taxonomy_for_object_type
wp_get_object_terms
wp_remove_object_terms
wp_set_object_terms
wp_insert_term
wp_update_term
wp_delete_term
wp_terms_checklist

The role of management and others

add_cap
add_role
author_can
current_user_can
current_user_can_for_blog
get_role
get_super_admins
is_super_admin
map_meta_cap
remove_cap
remove_role
user_can

Users and authors

auth_redirect
count_users
count_user_posts
count_many_users_posts
email_exists
get_currentuserinfo
get_current_user_id
get_profile
get_user_by
get_userdata
get_usernumposts
get_users
set_current_user
user_pass_ok
wp_authenticate
username_exists
validate_username
wp_dropdown_users
wp_get_current_user
wp_set_current_user
wp_set_password
get_author_posts_url
get_the_modified_author
is_multi_author

User meta

add_user_meta
delete_user_meta
get_user_meta
update_user_meta
get_the_author_meta

User registration and deletion

wp_create_user
wp_delete_user
wp_insert_user
wp_update_user

login / logout

is_user_logged_in
wp_login_form
wp_signon
wp_logout
wp_loginout
wp_logout_url

Feed function

bloginfo_rss
comment_author_rss
comment_link
comment_text_rss
do_feed
do_feed_atom
do_feed_rdf
do_feed_rss
do_feed_rss2
fetch_feed
fetch_rss
get_author_feed_link
get_bloginfo_rss
get_category_feed_link
get_comment_link
get_comment_author_rss
get_post_comments_feed_link
get_rss
get_search_comments_feed_link
get_search_feed_link
get_the_category_rss
get_the_title_rss
permalink_single_rss
post_comments_feed_link
rss_enclosure
the_title_rss
the_category_rss
the_content_rss
the_excerpt_rss
wp_rss

HTTP API functions

wp_remote_get
wp_remote_retrieve_body
wp_get_http_headers
wp_remote_fopen

Views, ping and tracking functions

add_ping
add_comment_meta
check_comment
comment_text
comment_form
comments_number
discover_pingback_server_uri
delete_comment_meta
do_all_pings
do_enclose
do_trackbacks
generic_ping
get_approved_comments
get_avatar
get_comment
get_comment_text
get_comment_meta
get_comments
wp_list_comments
get_enclosed
get_lastcommentmodified
get_pung
get_to_ping
have_comments
get_comment_author
is_trackback
pingback
privacy_ping_filter
sanitize_comment_cookies
trackback
trackback_url
trackback_url_list
update_comment_meta
weblog_ping
wp_allow_comment
wp_count_comments
wp_delete_comment
wp_filter_comment
wp_get_comment_status
wp_get_current_commenter
wp_insert_comment
wp_new_comment
wp_set_comment_status
wp_throttle_comment_flood
wp_update_comment
wp_update_comment_count
wp_update_comment_count_now

Comments functions

comment_class
comment_ID
comment_author
comment_date
comment_time
get_comment_date
get_comment_time

Pagination of comments

paginate_comments_links
previous_comments_link
next_comments_link
get_comment_pages_count

Functions of filters

has_filter
add_filter
apply_filters
apply_filters_ref_array
current_filter
merge_filters
remove_filter
remove_all_filters

Functions of actions

has_action
add_action
do_action
do_action_ref_array
did_action
remove_action
remove_all_actions

Functions of plugins

plugin_basename
plugins_url
get_plugin_data
get_admin_page_title
plugin_dir_path
register_activation_hook
register_deactivation_hook
menu_page_url
is_plugin_active
is_plugin_active_for_network
is_plugin_inactive
is_plugin_page
add_contextual_help
get_plugins

Widgets

is_active_widget
register_widget
the_widget
unregister_widget
wp_add_dashboard_widget
wp_convert_widget_settings
wp_get_sidebars_widgets
wp_get_widget_defaults
wp_register_sidebar_widget
wp_register_widget_control
wp_set_sidebars_widgets
wp_unregister_sidebar_widget
wp_unregister_widget_control
wp_widget_description

Settings

register_setting
unregister_setting
settings_fields
do_settings_fields
do_settings_sections
add_settings_field
add_settings_section
add_settings_error
get_settings_errors
settings_errors

Shortcodes

add_shortcode
do_shortcode
do_shortcode_tag
get_shortcode_regex
remove_shortcode
remove_all_shortcodes
shortcode_atts
shortcode_parse_atts
strip_shortcodes

Format related functions

comments_template
get_footer
get_header
get_sidebar
get_search_form

Other functions

add_custom_background
add_custom_image_header
add_image_size
add_theme_support
body_class
current_theme_supports
dynamic_sidebar
get_404_template
get_archive_template
get_attachment_template
get_author_template
get_body_class
get_category_template
get_comments_popup_template
get_current_theme
get_date_template
get_header_image
get_header_textcolor
get_home_template
get_locale_stylesheet_uri
get_page_template
get_paged_template
get_post_class
get_query_template
get_search_template
get_single_template
get_stylesheet
get_stylesheet_directory
get_stylesheet_directory_uri
get_stylesheet_uri
get_tag_template
get_taxonomy_template
get_template
get_template_directory
get_template_directory_uri
get_theme_file_uri
get_theme_file_path
get_template_part
get_theme
wp_get_themes
get_theme_data
get_theme_support
get_theme_mod
get_theme_mods
get_theme_root
get_theme_roots
get_theme_root_uri
get_themes
has_header_image
header_image
header_textcolor
in_the_loop
is_child_theme
is_active_sidebar
is_admin_bar_showing
is_customize_preview
is_dynamic_sidebar
language_attributes
load_template
locale_stylesheet
locate_template
post_class
preview_theme
preview_theme_ob_filter
preview_theme_ob_filter_callback
register_nav_menu
register_nav_menus
get_registered_nav_menus
wp_create_nav_menu
register_sidebar
register_sidebars
register_theme_directory
remove_theme_mod
remove_theme_mods
remove_theme_support
require_if_theme_supports
search_theme_directories
set_theme_mod
switch_theme
validate_current_theme
unregister_nav_menu
unregister_sidebar
wp_add_inline_style
wp_clean_themes_cache
wp_get_archives
wp_get_nav_menu_items
wp_get_theme
wp_nav_menu
wp_oembed_remove_provider
wp_page_menu
wp_title

Formatting functions

absint
add_magic_quotes
addslashes_gpc
antispambot
attribute_escape
backslashit
balanceTags
clean_pre
clean_url
convert_chars
convert_smilies
ent2ncr
esc_attr
esc_html
esc_js
esc_textarea
esc_sql
esc_url
esc_url_raw
force_balance_tags
format_to_edit
format_to_post
funky_javascript_fix
htmlentities2
is_email
js_escape
make_clickable
popuplinks
remove_accents
sanitize_email
sanitize_file_name
sanitize_html_class
sanitize_key
sanitize_mime_type
sanitize_option
sanitize_sql_orderby
sanitize_text_field
sanitize_title
sanitize_title_for_query
sanitize_title_with_dashes
sanitize_user
seems_utf8
stripslashes_deep
trailingslashit
untrailingslashit
urlencode_deep
url_shorten
utf8_uri_encode
wpautop
wptexturize
wp_filter_kses
wp_filter_post_kses
wp_filter_nohtml_kses
wp_iso_descrambler
wp_kses
wp_kses_array_lc
wp_kses_attr
wp_kses_bad_protocol
wp_kses_bad_protocol_once
wp_kses_bad_protocol_once2
wp_kses_check_attr_val
wp_kses_decode_entities
wp_kses_hair
wp_kses_hook
wp_kses_html_error
wp_kses_js_entities
wp_kses_no_null
wp_kses_normalize_entities
wp_kses_normalize_entities2
wp_kses_post
wp_kses_split
wp_kses_split2
wp_kses_stripslashes
wp_kses_version
wp_make_link_relative
wp_normalize_path
wp_rel_nofollow
wp_richedit_pre
wp_specialchars
wp_trim_words
zeroise

The importance of functions on WordPress

All WordPress themes come with a powerful functions.php file. This file acts as a plugin and allows you to do many things on your WordPress site. Changes that can create a huge transformation in your site.

Changing these codes requires sufficient knowledge of PHP. If you don't have experience working with them, we suggest you get help from experienced people.

We hope this article from KeyUpSeo blog was useful for you in getting to know the functions of WordPress.

Release date : 13 June, 2024