# WordPress Quick Reference *Themes, hooks, queries, REST API, custom post types* > Source: WordPress Developer Resources (developer.wordpress.org) ยท MIT ## Theme Basics ### Required Files | Command | Description | |---------|-------------| | `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 | Command | Description | |---------|-------------| | `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) | Command | Description | |---------|-------------| | `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 | Command | Description | |---------|-------------| | `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(); $thumb = get_the_post_thumbnail_url(null, 'medium'); ``` ## Custom Post Types ### Register CPT ``` add_action('init', function() { register_post_type('product', [ 'labels' => ['name' => 'Products', 'singular_name' => 'Product'], 'public' => true, 'has_archive' => true, 'supports' => ['title', 'editor', 'thumbnail'], ]); }); ``` ### Custom Taxonomy ``` register_taxonomy('brand', 'product', [ 'labels' => ['name' => 'Brands'], 'hierarchical' => true, 'rewrite' => ['slug' => 'brand'], ]); ``` ### Supports Options | Command | Description | |---------|-------------| | `title` | Post title field | | `editor` | Content editor | | `thumbnail` | Featured image | | `excerpt` | Excerpt field | | `custom-fields` | Meta box for custom fields | | `page-attributes` | Menu order, parent | | `revisions` | Revision history | ## Hooks & Filters ### Actions (Do Something) ``` // Register a hook add_action('wp_head', 'my_analytics', 20); function my_analytics() { echo ''; } ``` ### Filters (Modify Data) ``` // Modify the excerpt length add_filter('excerpt_length', fn() => 30); // Append text to every post add_filter('the_content', function($c) { return is_single() ? $c . '

Thanks for reading!

' : $c; }); ``` ### Key Hooks | Command | Description | |---------|-------------| | `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 | Command | Description | |---------|-------------| | `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()) { $q->set('posts_per_page', 5); } }); ``` ## REST API ### Built-in Endpoints | Command | Description | |---------|-------------| | `/wp-json/wp/v2/posts` | List / create posts | | `/wp-json/wp/v2/posts/{id}` | Get / update / delete post | | `/wp-json/wp/v2/pages` | Pages endpoint | | `/wp-json/wp/v2/categories` | Categories endpoint | | `/wp-json/wp/v2/media` | Media library | | `/wp-json/wp/v2/users` | Users endpoint | ### Custom Endpoint ``` add_action('rest_api_init', function() { register_rest_route('myplugin/v1', '/items', [ 'methods' => 'GET', 'callback' => fn($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 | Command | Description | |---------|-------------| | `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, $v)` | Set custom field value | ### User & Auth | Command | Description | |---------|-------------| | `wp_get_current_user()` | Current logged-in user | | `is_user_logged_in()` | Check login status | | `current_user_can($cap)` | Check capability | | `wp_create_nonce($action)` | Generate security nonce | | `wp_verify_nonce($nonce, $a)` | Verify nonce | ### Utility Functions | Command | Description | |---------|-------------| | `esc_html($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($val)` | Absolute integer | ## Enqueue ### Enqueue Styles & Scripts ``` add_action('wp_enqueue_scripts', function() { wp_enqueue_style('theme-style', get_stylesheet_uri(), [], '1.0'); wp_enqueue_script('theme-js', get_theme_file_uri('/js/app.js'), ['jquery'], '1.0', true); }); ``` ### Enqueue Functions | Command | Description | |---------|-------------| | `wp_enqueue_style($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"] ```