Functions – wordpressreference.com

Actions & Filters — Hooks

hook

add_action()

Hooks a function to a specific action. The backbone of WP’s event-driven system.

add_action( ‘init’, ‘my_custom_init’ ); function my_custom_init() { // runs on init }

hook

add_filter()

Hooks a function to modify data before it’s used by WordPress or returned to the browser.

add_filter( ‘the_title’, ‘prefix_title’ ); function prefix_title( $title ) { return ‘★ ‘ . $title; }

hook

do_action()

Executes all functions attached to a given action hook.

do_action( ‘my_plugin_loaded’ );

hook

apply_filters()

Calls all functions attached to a filter hook and returns the modified value.

$value = apply_filters( ‘my_plugin_value’, $raw );

hook

remove_action()

Removes a function from a specified action hook.

remove_action( ‘wp_head’, ‘wp_generator’ );

hook

has_action()

Checks if any function has been registered for an action.

if ( has_action( ‘init’, ‘my_fn’ ) ) { // it’s registered }

Queries & Posts

query

WP_Query()

The main class for fetching posts with full control over args, tax, meta, and ordering.

$q = new WP_Query([ ‘post_type’ => ‘post’, ‘posts_per_page’ => 5, ]); if ( $q->have_posts() ) { while ( $q->have_posts() ) { $q->the_post(); } } wp_reset_postdata();

query

get_posts()

Returns an array of post objects matching given criteria. Simpler alternative to WP_Query.

$posts = get_posts([ ‘post_type’ => ‘page’, ‘numberposts’ => 10, ]);

query

get_post()

Retrieves post data given a post ID, object, or array.

$post = get_post( 42 ); echo $post->post_title;

query

get_the_ID()

Retrieves the ID of the current post in The Loop.

$id = get_the_ID();

query

wp_insert_post()

Insert or update a post in the database.

$id = wp_insert_post([ ‘post_title’ => ‘Hello’, ‘post_status’ => ‘publish’, ‘post_content’ => ‘World!’, ]);

query

wp_delete_post()

Trashes or permanently deletes a post, and all associated data.

wp_delete_post( $post_id, true );

Theme & Template

theme

get_template_part()

Loads a template part into a template. Enables modular, reusable template components.

get_template_part( ‘template-parts/content’, ‘single’ );

theme

wp_enqueue_script()

Safely enqueue a JavaScript file. Handles dependencies and version control.

wp_enqueue_script( ‘my-script’, get_template_directory_uri() . ‘/js/app.js’, [‘jquery’], ‘1.0’, true );

theme

wp_enqueue_style()

Safely enqueue a CSS stylesheet with dependency management.

wp_enqueue_style( ‘my-style’, get_stylesheet_uri() );

theme

add_theme_support()

Registers support for various theme features like post thumbnails, custom logo, etc.

add_theme_support( ‘post-thumbnails’ ); add_theme_support( ‘custom-logo’ );

theme

register_nav_menus()

Registers navigation menu locations for a theme.

register_nav_menus([ ‘primary’ => ‘Primary Menu’, ‘footer’ => ‘Footer Menu’, ]);

theme

the_post_thumbnail()

Displays the post’s featured image, with optional size arg.

the_post_thumbnail( ‘medium_large’ );

Utilities & Options

utility

get_option()

Retrieves an option value from the options table.

$email = get_option( ‘admin_email’, ‘[email protected]’ );

utility

update_option()

Updates the value of an option in the options table.

update_option( ‘my_key’, ‘my_value’ );

utility

wp_redirect()

Redirects the user to a specified URL. Always follow with exit.

wp_redirect( home_url(‘/thanks/’) ); exit;

utility

sanitize_text_field()

Checks and cleans a string from user input. Removes tags, extra whitespace, invalid UTF-8.

$clean = sanitize_text_field( $_POST[‘name’] );

utility

esc_html()

Escapes HTML for safe output. Prevents XSS by encoding special characters.

echo esc_html( $user_input );

utility

wp_nonce_field()

Generates a hidden nonce field for form security verification.

wp_nonce_field( ‘my_action’, ‘my_nonce_field’ );

Post Meta & Taxonomies

meta

get_post_meta()

Retrieves a post’s meta field value. Pass true as the third arg for a single value.

$val = get_post_meta( $post_id, ‘_my_key’, true );

meta

update_post_meta()

Updates a post meta field. Creates it if it doesn’t exist.

update_post_meta( $post_id, ‘_my_key’, $value );

meta

register_post_type()

Registers a custom post type with all its labels, capabilities, and settings.

register_post_type( ‘project’, [ ‘label’ => ‘Projects’, ‘public’ => true, ‘supports’ => [‘title’,’editor’], ]);

meta

register_taxonomy()

Registers a custom taxonomy and links it to one or more post types.

register_taxonomy( ‘genre’, ‘project’, [ ‘label’ => ‘Genres’, ‘public’ => true ] );

meta

get_the_terms()

Returns terms attached to the given post for a given taxonomy.

$genres = get_the_terms( $post_id, ‘genre’ );

meta

wp_set_post_terms()

Assigns terms to a post for a specified taxonomy.

wp_set_post_terms( $post_id, [12, 15], ‘genre’ );

Users & Authentication

user

get_current_user_id()

Returns the ID of the currently logged-in user, or 0 if not logged in.

$uid = get_current_user_id(); if ( $uid ) { /* logged in */ }

user

current_user_can()

Checks if the current user has a specific capability or role.

if ( current_user_can( ‘edit_posts’ ) ) { // user can edit }

user

wp_get_current_user()

Returns a WP_User object for the current user.

$user = wp_get_current_user(); echo $user->user_email;

user

get_user_meta()

Retrieves metadata for the specified user.

$city = get_user_meta( $user_id, ‘city’, true );

⚠ Pro Tips

Always use wp_reset_postdata() after a custom WP_Query loop to restore the global $post object.
Never trust user input — always sanitize on input (sanitize_*()) and escape on output (esc_*()).
Use nonces (wp_create_nonce() / check_admin_referer()) for all forms and AJAX calls.
Avoid direct database queries — use the WP functions and WP_Query first for caching and hook benefits.
Use wp_schedule_event() for recurring background tasks instead of cron jobs where possible.