Theme Basics

Required Files

style.css	Theme metadata header + styles
index.php	Fallback template (required)
functions.php	Theme setup, hooks, enqueue
screenshot.png	Theme preview (1200x900)

style.css Header

/*
Theme Name: My Theme
Theme URI: https://example.com
Version: 1.0
Requires at least: 6.0
*/

functions.php Setup

add_action('after_setup_theme', function() {
    add_theme_support('title-tag');
    add_theme_support('post-thumbnails');
    add_theme_support('html5', ['search-form', 'gallery']);
    register_nav_menus(['primary' => 'Main Nav']);
});

Template Hierarchy

Page Templates

front-page.php	Static front page
home.php	Blog posts index
single.php	Single post
page.php	Single page
archive.php	Post archives (date, category)
category.php	Category archive
search.php	Search results
404.php	Not found
index.php	Ultimate fallback

Template Parts

get_header();            // header.php
get_footer();            // footer.php
get_sidebar();           // sidebar.php
get_template_part('parts/card'); // parts/card.php
get_template_part('parts/card', 'featured');

Lookup Order (Single Post)

1	single-{post_type}-{slug}.php
2	single-{post_type}.php
3	single.php
4	singular.php
5	index.php

The Loop

Standard Loop

Template Tags

the_title()	Print post title
the_content()	Print post content
the_excerpt()	Print post excerpt
the_permalink()	Print post URL
the_post_thumbnail()	Print featured image
the_date()	Print publish date
the_author()	Print author name
the_category()	Print category links

Getters (Return, Not Print)

$title = get_the_title();
$url   = get_permalink();
$id    = get_the_ID();
$thumb = get_the_post_thumbnail_url(null, 'medium');

Custom Post Types

add_action('init', function() {
    register_post_type('product', [
        'labels'  => ['name' => 'Products', 'singular_name' => 'Product'],
        'public'  => true,
        'has_archive' => true,
        'supports' => ['title', 'editor', 'thumbnail'],
    ]);
});

Custom Taxonomy

register_taxonomy('brand', 'product', [
    'labels'       => ['name' => 'Brands'],
    'hierarchical' => true,
    'rewrite'      => ['slug' => 'brand'],
]);

Supports Options

title	Post title field
editor	Content editor
thumbnail	Featured image
excerpt	Excerpt field
custom-fields	Meta box for custom fields
page-attributes	Menu order, parent
revisions	Revision history

Hooks & Filters

Actions (Do Something)

// Register a hook
add_action('wp_head', 'my_analytics', 20);
function my_analytics() {
    echo '';
}

Filters (Modify Data)

// Modify the excerpt length add_filter('excerpt_length', fn() => 30); // Append text to every post add_filter('the_content', function($c) { return is_single() ? $c . '

Thanks for reading!

' : $c; });

Key Hooks

init	WP initialized; register CPTs here
wp_enqueue_scripts	Enqueue CSS/JS
wp_head	Output in
wp_footer	Output before
save_post	After a post is saved
pre_get_posts	Modify main query before execution
the_content	Filter post content output
the_title	Filter post title output

WP_Query

Custom Query

$q = new WP_Query([
    'post_type'      => 'product',
    'posts_per_page' => 10,
    'orderby'        => 'date',
    'order'          => 'DESC',
]);
while ($q->have_posts()) : $q->the_post();
    the_title('', '');
endwhile; wp_reset_postdata();

Common Parameters

post_type	post, page, or custom type
posts_per_page	Number of results (-1 for all)
category_name	Filter by category slug
tag	Filter by tag slug
s	Search keyword
meta_key / meta_value	Filter by custom field
tax_query	Advanced taxonomy filtering
date_query	Filter by date range

Modify Main Query

add_action('pre_get_posts', function($q) {
    if (!is_admin() && $q->is_main_query() && is_home()) {
        $q->set('posts_per_page', 5);
    }
});

REST API

Built-in Endpoints

/wp-json/wp/v2/posts	List / create posts
/wp-json/wp/v2/posts/{id}	Get / update / delete post
/wp-json/wp/v2/pages	Pages endpoint
/wp-json/wp/v2/categories	Categories endpoint
/wp-json/wp/v2/media	Media library
/wp-json/wp/v2/users	Users endpoint

Custom Endpoint

add_action('rest_api_init', function() {
    register_rest_route('myplugin/v1', '/items', [
        'methods'  => 'GET',
        'callback' => fn($req) => new WP_REST_Response(
            get_posts(['post_type' => 'item', 'numberposts' => 20])
        ),
        'permission_callback' => '__return_true',
    ]);
});

Fetch from JavaScript

const res = await fetch('/wp-json/wp/v2/posts?per_page=5');
const posts = await res.json();
posts.forEach(p => console.log(p.title.rendered));

Functions

Post Functions

get_posts($args)	Retrieve array of posts
wp_insert_post($arr)	Create or update a post
wp_delete_post($id)	Trash or delete a post
get_post_meta($id, $key)	Get custom field value
update_post_meta($id, $k, $v)	Set custom field value

User & Auth

wp_get_current_user()	Current logged-in user
is_user_logged_in()	Check login status
current_user_can($cap)	Check capability
wp_create_nonce($action)	Generate security nonce
wp_verify_nonce($nonce, $a)	Verify nonce

Utility Functions

esc_html($str)	Escape for HTML context
esc_attr($str)	Escape for attribute context
esc_url($url)	Sanitize URL
wp_kses_post($html)	Allow only safe post HTML
sanitize_text_field($s)	Strip tags and extra whitespace
absint($val)	Absolute integer

Enqueue

Enqueue Styles & Scripts

add_action('wp_enqueue_scripts', function() {
    wp_enqueue_style('theme-style', get_stylesheet_uri(), [], '1.0');
    wp_enqueue_script('theme-js', get_theme_file_uri('/js/app.js'),
        ['jquery'], '1.0', true);
});

Enqueue Functions

wp_enqueue_style($h, $src)	Register + enqueue CSS
wp_enqueue_script($h, $src)	Register + enqueue JS
wp_localize_script($h, $n, $d)	Pass PHP data to JS
wp_dequeue_style($handle)	Remove enqueued style
wp_dequeue_script($handle)	Remove enqueued script

Pass Data to JavaScript

wp_enqueue_script('my-app', get_theme_file_uri('/js/app.js'));
wp_localize_script('my-app', 'myData', [
    'ajaxUrl' => admin_url('admin-ajax.php'),
    'nonce'   => wp_create_nonce('my_action'),
]);
// JS: console.log(myData.ajaxUrl)

Common Patterns

Custom Page Template

AJAX Handler

add_action('wp_ajax_my_action', 'handle_my_action');
add_action('wp_ajax_nopriv_my_action', 'handle_my_action');
function handle_my_action() {
    check_ajax_referer('my_action', 'nonce');
    wp_send_json_success(['msg' => 'OK']);
}

Shortcode

add_shortcode('greeting', function($atts) { $a = shortcode_atts(['name' => 'World'], $atts); return '

Hello, ' . esc_html($a['name']) . '!

'; }); // Usage: [greeting name="Zhi"]

WORDPRESS QUICK REFERENCE

', '