php functions list wordpress

The Loop Functions

The core of WordPress for displaying post content. These are used inside the main post loop.

have_posts() - Checks if there are any posts to display in the current query.
```
<?php if ( have_posts() ) : ?>
```
the_post() - Sets up the current post's data, making it available for use.
```
<?php while ( have_posts() ) : the_post(); ?>
```
the_ID() - Displays the numeric ID of the current post.
```
<p>Post ID: <?php the_ID(); ?></p>
```
get_the_ID() - Returns the numeric ID of the current post for use in a variable.
```
<?php $current_post_id = get_the_ID(); ?>
```
the_title() - Displays the title of the current post.
```
<h2><?php the_title(); ?></h2>
```
get_the_title() - Returns the title of the current post for use in a variable.
```
<?php $post_title = get_the_title(); ?>
```
the_content() - Displays the full content of the current post.
```
<div class="entry-content"><?php the_content(); ?></div>
```
the_excerpt() - Displays a brief summary (excerpt) of the current post.
```
<div class="entry-summary"><?php the_excerpt(); ?></div>
```
the_permalink() - Displays the full URL of the current post.
```
<a href="<?php the_permalink(); ?>">Read More</a>
```
the_author() - Displays the display name of the current post's author.
```
<p>By <?php the_author(); ?></p>
```
the_author_posts_link() - Displays the author's name linked to their post archive.
```
<div class="post-author"><?php the_author_posts_link(); ?></div>
```
the_date() - Displays the publication date of the current post.
```
<span class="post-date"><?php the_date('F j, Y'); ?></span>
```
the_category() - Displays the categories of the current post as a link.
```
<div class="post-categories"><?php the_category(', '); ?></div>
```

the_tags() - Displays the tags of the current post as links.

<div class="post-tags"><?php the_tags('Tags: ', ', ', ''); ?></div>

rewind_posts() - Resets the loop, allowing you to run it again on the same page.
```
<?php rewind_posts(); ?>
```

Theme & Template Functions

Functions for building and managing theme structure and assets.

get_header() - Includes the `header.php` template file.
```
<?php get_header(); ?>
```
get_footer() - Includes the `footer.php` template file.
```
<?php get_footer(); ?>
```

get_sidebar() - Includes the `sidebar.php` template file.

<?php get_sidebar('primary'); // Includes sidebar-primary.php if it exists ?>

get_template_part() - Loads a specified template part file.

<?php get_template_part('template-parts/content', get_post_type()); ?>

get_search_form() - Includes the `searchform.php` template file.
```
<?php get_search_form(); ?>
```
wp_head() - Fires the `wp_head` action hook; essential for plugins.
```
<?php wp_head(); ?>
```
wp_footer() - Fires the `wp_footer` action hook; essential for plugins.
```
<?php wp_footer(); ?>
```
body_class() - Displays CSS classes for the `` tag, based on the current page.
```
<body <?php body_class(); ?>>
```

wp_enqueue_style() - Safely adds a CSS stylesheet to the page.

function my_theme_styles() { wp_enqueue_style( 'my-custom-style', get_template_directory_uri() . '/css/custom.css' ); }
add_action( 'wp_enqueue_scripts', 'my_theme_styles' );

wp_enqueue_script() - Safely adds a JavaScript file to the page.

function my_theme_scripts() { wp_enqueue_script( 'my-custom-script', get_template_directory_uri() . '/js/custom.js', array('jquery'), null, true ); }
add_action( 'wp_enqueue_scripts', 'my_theme_scripts' );

get_stylesheet_directory_uri() - Retrieves the URI of the active theme's (child theme) directory.
```
<img src="<?php echo get_stylesheet_directory_uri(); ?>/images/logo.png">
```

get_template_directory_uri() - Retrieves the URI of the parent theme's directory.

<script src="<?php echo get_template_directory_uri(); ?>/js/parent-theme.js"></script>

add_theme_support() - Registers theme support for a given feature (e.g., post thumbnails, title tag).

function theme_setup() { add_theme_support( 'post-thumbnails' ); }
add_action( 'after_setup_theme', 'theme_setup' );

register_nav_menus() - Registers multiple navigation menu locations for a theme.

function register_my_menus() { register_nav_menus( array( 'primary' => __( 'Primary Menu' ), 'footer' => __( 'Footer Menu' ) ) ); }
add_action( 'init', 'register_my_menus' );

wp_nav_menu() - Displays a navigation menu created in the admin dashboard.
```
<?php wp_nav_menu( array( 'theme_location' => 'primary' ) ); ?>
```

register_sidebar() - Registers a widget area (sidebar) for the theme.

function my_register_sidebars() { register_sidebar(array('id' => 'primary', 'name' => 'Primary Sidebar')); }
add_action( 'widgets_init', 'my_register_sidebars' );

dynamic_sidebar() - Displays the widgets assigned to a specific sidebar.

<?php if ( is_active_sidebar( 'primary' ) ) : dynamic_sidebar( 'primary' ); endif; ?>

Post & Page Functions

Functions for retrieving and managing data about posts, pages, and custom post types.

get_post() - Retrieves post data for a given post ID.

<?php $my_post = get_post(123); echo $my_post->post_title; ?>

get_posts() - Retrieves an array of post objects based on specified criteria.

<?php $args = array( 'posts_per_page' => 5 ); $latest_posts = get_posts( $args ); ?>

wp_insert_post() - Inserts a new post into the database.

<?php $new_post = array('post_title' => 'My New Post', 'post_content' => 'This is the content.', 'post_status' => 'publish');
$post_id = wp_insert_post($new_post); ?>

has_post_thumbnail() - Checks if the current post has a featured image.
```
<?php if ( has_post_thumbnail() ) { // Display the thumbnail } ?>
```

the_post_thumbnail() - Displays the featured image of the current post.

<?php the_post_thumbnail('thumbnail'); // Options: thumbnail, medium, large, full ?>

get_the_post_thumbnail_url() - Returns the URL of the featured image.

<?php $image_url = get_the_post_thumbnail_url(get_the_ID(), 'full'); ?>

get_post_meta() - Retrieves a custom field (post meta) value for a post.

<?php $custom_field = get_post_meta(get_the_ID(), 'my_custom_field_key', true); ?>

update_post_meta() - Updates a custom field value for a post.

<?php update_post_meta(123, 'my_custom_field_key', 'New Value'); ?>

get_permalink() - Retrieves the permalink for a post by its ID.
```
<?php echo get_permalink(123); ?>
```

next_post_link() - Displays a link to the next post on a single post page.

<div class="nav-next"><?php next_post_link( '%link', 'Next Post »' ); ?></div>

previous_post_link() - Displays a link to the previous post on a single post page.

<div class="nav-previous"><?php previous_post_link( '%link', '« Previous Post' ); ?></div>

Conditional Tags

Functions that check for a specific condition and return TRUE or FALSE. Often used with `if` statements.

is_front_page() - Checks if the main front page is being displayed.

<?php if ( is_front_page() ) { /* Front page specific code */ } ?>

is_home() - Checks if the blog posts index is being displayed.

<?php if ( is_home() && ! is_front_page() ) { /* Blog page specific code */ } ?>

is_single() - Checks if a single post of any post type is being displayed.
```
<?php if ( is_single() ) { /* Single post specific code */ } ?>
```

is_page() - Checks if a specific static Page is being displayed.

<?php if ( is_page('contact-us') ) { /* Contact page specific code */ } ?>

is_category() - Checks if a category archive page is being displayed.

<?php if ( is_category('news') ) { /* News category specific code */ } ?>

is_tag() - Checks if a tag archive page is being displayed.
```
<?php if ( is_tag() ) { /* Any tag archive page */ } ?>
```
is_author() - Checks if an author archive page is being displayed.
```
<?php if ( is_author(4) ) { /* Code for author with ID 4 */ } ?>
```
is_archive() - Checks if any type of archive page is being displayed.
```
<?php if ( is_archive() ) { /* General archive page code */ } ?>
```
is_search() - Checks if a search results page is being displayed.
```
<?php if ( is_search() ) { /* Search results page code */ } ?>
```
is_404() - Checks if a "404 Not Found" error page is being displayed.
```
<?php if ( is_404() ) { /* 404 page specific code */ } ?>
```

is_admin() - Checks if the administration dashboard is being displayed.

<?php if ( ! is_admin() ) { /* Code that runs only on the front-end */ } ?>

has_tag() - Checks if the current post has a specific tag.

<?php if ( has_tag('featured') ) { /* Featured post code */ } ?>

has_category() - Checks if the current post has a specific category.

<?php if ( has_category('tutorials') ) { /* Tutorial post code */ } ?>

is_active_sidebar() - Checks if a sidebar has active widgets.

<?php if ( is_active_sidebar( 'primary' ) ) { /* Code to display sidebar container */ } ?>

User Functions

Functions for managing and retrieving user data.

is_user_logged_in() - Checks if the current visitor is a logged-in user.

<?php if ( is_user_logged_in() ) { echo 'Welcome back!'; } else { echo 'Welcome, guest!'; } ?>

wp_get_current_user() - Retrieves the complete user object for the current user.

<?php $current_user = wp_get_current_user(); echo 'Username: ' . $current_user->user_login; ?>

get_current_user_id() - Returns the numeric ID of the current user.
```
<?php $user_id = get_current_user_id(); ?>
```
current_user_can() - Checks if the current user has a specific capability or role.
```
<?php if ( current_user_can('edit_posts') ) { echo 'You can edit posts.'; } ?>
```

get_avatar() - Displays the avatar for a user.

<?php echo get_avatar( get_the_author_meta('ID'), 64 ); // 64 is the size in pixels ?>

get_the_author_meta() - Retrieves a specific field from the author's profile.
```
<?php echo 'Author bio: ' . get_the_author_meta('description'); ?>
```

URL Functions

Functions for generating and retrieving URLs within WordPress.

home_url() - Retrieves the URL for the site's home page.

<a href="<?php echo esc_url( home_url( '/' ) ); ?>">Go Home</a>

site_url() - Retrieves the URL for the current site (where WordPress core files are located).
```
<?php echo site_url(); ?>
```

admin_url() - Retrieves the URL to the admin area.

<a href="<?php echo esc_url( admin_url( 'profile.php' ) ); ?>">Edit Profile</a>

includes_url() - Retrieves the URL to the includes directory.
```
<?php echo includes_url(); ?>
```
content_url() - Retrieves the URL to the content directory (`wp-content`).
```
<?php echo content_url(); ?>
```

plugins_url() - Retrieves the URL to the plugins directory.

<img src="<?php echo plugins_url( 'my-plugin/images/icon.png' ); ?>">

Database & Options Functions

Functions for interacting directly with the WordPress database and the options table.

get_option() - Retrieves a value from the `wp_options` table.

<?php $blog_description = get_option( 'blogdescription' ); ?>

update_option() - Updates a value in the `wp_options` table.

<?php update_option( 'my_custom_setting', 'new_value' ); ?>

get_bloginfo() - Retrieves information about the current site, like its name or URL.
```
<h1><?php bloginfo('name'); ?></h1>
```

$wpdb - The global WordPress database object for custom database queries.

global $wpdb;
$results = $wpdb->get_results("SELECT * FROM {$wpdb->prefix}posts WHERE post_status = 'publish'");

Hooks: Actions and Filters

Functions that allow you to "hook" your custom code into WordPress execution at specific points.

add_action() - Hooks a function to a specific action.

// In functions.php:
function my_custom_function() { /* do something */ }
add_action('wp_head', 'my_custom_function');

add_filter() - Hooks a function to a specific filter to modify data.

// In functions.php:
function change_excerpt_length($length) { return 20; } // 20 words
add_filter('excerpt_length', 'change_excerpt_length');

do_action() - Executes all functions hooked to a specific action.
```
<?php do_action('my_custom_action_before_footer'); ?>
```

apply_filters() - Applies all filters hooked to a specific tag.

// In a plugin or theme:
$title = apply_filters('my_custom_title', 'Default Title');

WordPress PHP Functions Cheat Sheet