WordPress cheat sheet

archive.php

<?php

/**
 * Check page is category.
 */
if ( is_category() && $term = get_queried_object() ) {
    print_r($term);
}

form.php

<?php

/**
 * Security form.
 */

// Render nonce in form.
wp_nonce_field( basename( __FILE__ ), 'custom_nonce' );

// Check security.
if ( ! wp_verify_nonce( $_POST['custom_nonce'], basename( __FILE__ ) ) ) {
    return '<p>Failed.</p>';
}
if ( ! current_user_can( 'manage_options' ) )
    return '<p>Failed.</p>';
}

menu.php

<?php

function themename_admin_menu() {
    $parent_slug = 'themename-options';
    add_menu_page( 'Theme Options', 'General Options', 'manage_options', $parent_slug, 'themename_menu_options_general' );
    add_submenu_page( $parent_slug, 'Submenu', 'Submenu Options', 'manage_options', $parent_slug .'-submenu', 'themename_menu_options_submenu' );
    
    // Change first submenu title to 'General'.
    global $submenu;
    if ( isset( $submenu[ $parent_slug ] ) && count( $submenu[ $parent_slug ] ) > 0 ) {
        $submenu[ $parent_slug ][0][0] = 'General';
    }
}
add_action( 'admin_menu', 'themename_admin_menu' );

posts.php

<?php

/**
 * Get posts by custom taxonomy.
 */
$posts = get_posts( array(
    'tax_query' => array(
        array(
            'taxonomy' => 'custom_taxonomy',
            'field' => 'id', // id, slug
            'terms' => array(1, 2, 3), // Can be string ('1,2,3'), int (1), or array
        ),
    ),
) );

/**
 * Get posts by specific posts.
 */
$post_ids = array(1, 2, 3);
$posts = get_posts( array(
    'post__in' => $post_ids,
    'orderby' => 'post__in',
    'posts_per_page' => count( $post_ids ),
) );

/**
 * Save post.
 */
$post = get_post( 1 );
$post->post_title = $post->post_title . ' (Updated)';
wp_update_post( $post );

template.php

<?php

/**
 * Get posts in template.
 */
query_posts( array(
    'post_type' => 'post',
    'tax_query' => array(
        array(
            'taxonomy' => 'custom_taxonomy',
            'field' => 'id', // id, slug
            'terms' => array(1, 2, 3), // Can be string ('1,2,3'), int (1), or array
        ),
    ),
) );
while ( have_posts() ):
    the_post(); // This is important to call the_*() especially the_excerpt(). 
    // Do your thing.
endwhile;

/**
 * Set variable to template file.
 */
set_query_var( 'variable_name', 'value go here' );
// archive.php
echo $variable_name; // print 'value go here'

/**
 * Output pagination.
 */
function the_pagination( $query = null ) {
    if ( !$query ) {
        global $wp_query;
        $query = $wp_query;
    }
    $big = 999999999;
    $links = paginate_links( array(
        'base' => str_replace( $big, '%#%', esc_url( get_pagenum_link( $big ) ) ),
        'format' => '?paged=%#%',
        'current' => max( 1, get_query_var( 'paged' ) ),
        'total' => $query->max_num_pages,
        'next_text' => 'Next <span>&rsaquo;</span>',
        'prev_text' => '<span>&lsaquo;</span> Prev',
        'type' => 'array',
    ) );

    if ( $links ) {
        echo '<ul class="pagination"><li>'. implode('</li><li>', $links) .'</li></ul>';
    }
}

terms.php

<?php

/**
 * Get categories by custom taxonomy.
 */
$categories = get_categories( array(
    'taxonomy' => 'custom_taxonomy',
    'hide_empty' => false,
) );

/**
 * Get single term object.
 */
$term = get_term( $id_or_slug );

/**
 * Get categories in post.
 */
$categories = get_the_category( $post_id );

/**
 * Get custom taxonomny's terms in post.
 */
$terms = get_the_terms( $post_id, 'custom_taxonomy' ); // default taxonomy is 'category'.

/**
 * Remove terms from post.
 */
$terms = array(1, 2, 3);
$terms = '1,2,3';
$terms = 1;
wp_remove_object_terms( $post_id, $terms, 'custom_taxonomy' );

/**
 * Add categories to post.
 */
$categories = array(1, 2, 3);
$categories = '1,2,3';
$categories = 1;
wp_set_post_categories( $post_id, $categories );

/**
 * Add custom taxonomy's terms to post or custom post.
 */
$categories = array(1, 2, 3);
$categories = '1,2,3';
$categories = 1;
wp_set_object_terms( $post_id, $categories );

theme.php

<?php

/**
 * Setup theme.
 */
function your_theme_name_setup() {
    // Make theme available for translation.
    load_theme_textdomain( 'your_theme_text_domain' );

    // Add default posts and comments RSS feed links to head.
    add_theme_support( 'automatic-feed-links' );

    // Auto generate title tag.
    add_theme_support( 'title-tag' );

    // Enable support for Post Thumbnails on posts and pages.
    add_theme_support( 'post-thumbnails' );
    add_image_size( 'your-prefix-cover', 960, 720, array( '1', '' ) );
    add_image_size( 'your-prefix-large', 540, 405, array( '1', '' ) );
    add_image_size( 'your-prefix-thumbnail', 380, 285, array( '1', '' ) );

    // This theme uses wp_nav_menu() in two locations.
    add_theme_support( 'menus' );
    register_nav_menus( array(
        'top'    => __( 'Top Menu', 'your_theme_text_domain' ),
        'footer' => __( 'Footer Menu', 'your_theme_text_domain' ),
    ) );

    add_theme_support( 'widgets' );
}
add_action( 'after_setup_theme', 'your_theme_name_setup' );

utils.php

<?php

/**
 * Prevent from script run individually.
 */
if ( ! defined( 'ABSPATH' ) ) die( 'Nothing for you here.');

/**
 * Include file in theme.
 */
require_once get_stylesheet_directory() . '/path/to/file.php';

/**
 * Include file in base theme.
 */
require_once get_template_directory() . '/path/to/file.php';

/**
 * Output content from wp_editor().
 */
wpautop( $string_from_wp_editor );


/**
 * Print sql.
 */
function dump_request( $input ) {
    var_dump($input);
    return $input;
}
add_filter( 'posts_request', 'dump_request' );