How to Add Custom Post Types to WordPress Without Plugins

function dprt_register_portfolio() {
    register_post_type('portfolio', array(
        'labels' => array(
            'name' => 'Portfolio',
            'singular_name' => 'Portfolio Item',
            'add_new' => 'Add New Project',
            'add_new_item' => 'Add New Portfolio Item',
            'edit_item' => 'Edit Portfolio Item',
            'new_item' => 'New Portfolio Item',
            'view_item' => 'View Portfolio Item',
            'search_items' => 'Search Portfolio',
            'not_found' => 'No portfolio items found',
            'not_found_in_trash' => 'No portfolio items found in trash'
        ),
        'public' => true,
        'has_archive' => true,
        'rewrite' => array('slug' => 'portfolio'),
        'supports' => array('title', 'editor', 'thumbnail', 'excerpt'),
        'menu_icon' => 'dashicons-portfolio',
        'show_in_rest' => true, // Gutenberg support
    ));
}
add_action('init', 'dprt_register_portfolio');

// Visit Settings → Permalinks to flush, or run this code once:
flush_rewrite_rules();

array(
    'slug' => 'portfolio',
    'with_front' => false,
    'hierarchical' => false
)

function dprt_register_products() {
    $labels = array(
        'name' => _x('Products', 'Post type general name', 'textdomain'),
        'singular_name' => _x('Product', 'Post type singular name', 'textdomain'),
        'menu_name' => _x('Products', 'Admin Menu text', 'textdomain'),
        'name_admin_bar' => _x('Product', 'Add New on Toolbar', 'textdomain'),
        'add_new' => __('Add New', 'textdomain'),
        'add_new_item' => __('Add New Product', 'textdomain'),
        'new_item' => __('New Product', 'textdomain'),
        'edit_item' => __('Edit Product', 'textdomain'),
        'view_item' => __('View Product', 'textdomain'),
        'all_items' => __('All Products', 'textdomain'),
        'search_items' => __('Search Products', 'textdomain'),
        'parent_item_colon' => __('Parent Products:', 'textdomain'),
        'not_found' => __('No products found.', 'textdomain'),
        'not_found_in_trash' => __('No products found in Trash.', 'textdomain'),
        'featured_image' => _x('Product Image', 'Overrides the "Featured Image" phrase', 'textdomain'),
        'set_featured_image' => _x('Set product image', 'Overrides the "Set featured image" phrase', 'textdomain'),
        'remove_featured_image' => _x('Remove product image', 'Overrides the "Remove featured image" phrase', 'textdomain'),
        'use_featured_image' => _x('Use as product image', 'Overrides the "Use as featured image" phrase', 'textdomain'),
        'archives' => _x('Product archives', 'The post type archive label', 'textdomain'),
        'insert_into_item' => _x('Insert into product', 'Overrides the "Insert into post" phrase', 'textdomain'),
        'uploaded_to_this_item' => _x('Uploaded to this product', 'Overrides the "Uploaded to this post" phrase', 'textdomain'),
        'filter_items_list' => _x('Filter products list', 'Screen reader text', 'textdomain'),
        'items_list_navigation' => _x('Products list navigation', 'Screen reader text', 'textdomain'),
        'items_list' => _x('Products list', 'Screen reader text', 'textdomain'),
    );

    $args = array(
        'labels' => $labels,
        'public' => true,
        'publicly_queryable' => true,
        'show_ui' => true,
        'show_in_menu' => true,
        'query_var' => true,
        'rewrite' => array('slug' => 'product'),
        'capability_type' => 'post',
        'has_archive' => true,
        'hierarchical' => false,
        'menu_position' => 5,
        'menu_icon' => 'dashicons-products',
        'supports' => array('title', 'editor', 'thumbnail', 'excerpt', 'custom-fields'),
        'show_in_rest' => true,
        'rest_base' => 'products',
        'rest_controller_class' => 'WP_REST_Posts_Controller',
    );

    register_post_type('product', $args);
}
add_action('init', 'dprt_register_products');

function dprt_register_product_category() {
    register_taxonomy('product_category', 'product', array(
        'labels' => array(
            'name' => 'Product Categories',
            'singular_name' => 'Product Category',
            'search_items' => 'Search Categories',
            'all_items' => 'All Categories',
            'parent_item' => 'Parent Category',
            'parent_item_colon' => 'Parent Category:',
            'edit_item' => 'Edit Category',
            'update_item' => 'Update Category',
            'add_new_item' => 'Add New Category',
            'new_item_name' => 'New Category Name',
            'menu_name' => 'Categories',
        ),
        'hierarchical' => true, // Like categories
        'show_ui' => true,
        'show_admin_column' => true, // Show in admin post list
        'query_var' => true,
        'rewrite' => array('slug' => 'product-category'),
        'show_in_rest' => true,
    ));
}
add_action('init', 'dprt_register_product_category');

function dprt_register_product_tag() {
    register_taxonomy('product_tag', 'product', array(
        'labels' => array(
            'name' => 'Product Tags',
            'singular_name' => 'Product Tag',
            'search_items' => 'Search Tags',
            'all_items' => 'All Tags',
            'edit_item' => 'Edit Tag',
            'update_item' => 'Update Tag',
            'add_new_item' => 'Add New Tag',
            'new_item_name' => 'New Tag Name',
            'menu_name' => 'Tags',
        ),
        'hierarchical' => false, // Like tags
        'show_ui' => true,
        'show_admin_column' => true,
        'query_var' => true,
        'rewrite' => array('slug' => 'product-tag'),
        'show_in_rest' => true,
    ));
}
add_action('init', 'dprt_register_product_tag');

<?php get_header(); ?>

<main id="primary" class="site-main">
    <?php
    while (have_posts()) :
        the_post();
        ?>
        <article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
            <header class="entry-header">
                <h1 class="entry-title"><?php the_title(); ?></h1>
            </header>

            <?php if (has_post_thumbnail()) : ?>
                <div class="post-thumbnail">
                    <?php the_post_thumbnail('large'); ?>
                </div>
            <?php endif; ?>

            <div class="entry-content">
                <?php the_content(); ?>
            </div>

            <?php
            // Display custom taxonomy terms
            $categories = get_the_terms(get_the_ID(), 'portfolio_category');
            if ($categories && !is_wp_error($categories)) :
                ?>
                <div class="portfolio-categories">
                    <strong>Categories:</strong>
                    <?php
                    foreach ($categories as $category) {
                        echo '<span>' . esc_html($category->name) . '</span> ';
                    }
                    ?>
                </div>
            <?php endif; ?>
        </article>
    <?php endwhile; ?>
</main>

<?php get_footer(); ?>

<?php get_header(); ?>

<main id="primary" class="site-main">
    <header class="page-header">
        <h1 class="page-title">Portfolio</h1>
    </header>

    <?php if (have_posts()) : ?>
        <div class="portfolio-grid">
            <?php
            while (have_posts()) :
                the_post();
                ?>
                <article id="post-<?php the_ID(); ?>" <?php post_class('portfolio-item'); ?>>
                    <?php if (has_post_thumbnail()) : ?>
                        <a href="<?php the_permalink(); ?>">
                            <?php the_post_thumbnail('medium'); ?>
                        </a>
                    <?php endif; ?>

                    <h2 class="entry-title">
                        <a href="<?php the_permalink(); ?>"><?php the_title(); ?></a>
                    </h2>

                    <div class="entry-excerpt">
                        <?php the_excerpt(); ?>
                    </div>
                </article>
            <?php endwhile; ?>
        </div>

        <?php the_posts_pagination(); ?>

    <?php else : ?>
        <p>No portfolio items found.</p>
    <?php endif; ?>
</main>

<?php get_footer(); ?>

// Get all portfolio items
$portfolio = new WP_Query(array(
    'post_type' => 'portfolio',
    'posts_per_page' => 10,
));

// Get portfolio by category
$featured_portfolio = new WP_Query(array(
    'post_type' => 'portfolio',
    'posts_per_page' => 6,
    'tax_query' => array(
        array(
            'taxonomy' => 'portfolio_category',
            'field' => 'slug',
            'terms' => 'featured',
        ),
    ),
));

// Multiple post types
$mixed = new WP_Query(array(
    'post_type' => array('post', 'portfolio', 'product'),
    'posts_per_page' => 10,
));

// Custom field query
$expensive_products = new WP_Query(array(
    'post_type' => 'product',
    'meta_query' => array(
        array(
            'key' => 'price',
            'value' => 100,
            'compare' => '>',
            'type' => 'NUMERIC',
        ),
    ),
));

// Add custom columns
function dprt_portfolio_columns($columns) {
    $new_columns = array();
    $new_columns['cb'] = $columns['cb'];
    $new_columns['thumbnail'] = 'Image';
    $new_columns['title'] = $columns['title'];
    $new_columns['portfolio_category'] = 'Category';
    $new_columns['date'] = $columns['date'];
    return $new_columns;
}
add_filter('manage_portfolio_posts_columns', 'dprt_portfolio_columns');

// Populate custom columns
function dprt_portfolio_column_content($column, $post_id) {
    switch ($column) {
        case 'thumbnail':
            echo get_the_post_thumbnail($post_id, array(60, 60));
            break;

        case 'portfolio_category':
            $terms = get_the_terms($post_id, 'portfolio_category');
            if ($terms && !is_wp_error($terms)) {
                $term_names = wp_list_pluck($terms, 'name');
                echo implode(', ', $term_names);
            } else {
                echo '—';
            }
            break;
    }
}
add_action('manage_portfolio_posts_custom_column', 'dprt_portfolio_column_content', 10, 2);

// Make columns sortable
function dprt_sortable_columns($columns) {
    $columns['portfolio_category'] = 'portfolio_category';
    return $columns;
}
add_filter('manage_edit-portfolio_sortable_columns', 'dprt_sortable_columns');

function dprt_custom_permalinks($post_link, $post) {
    if ($post->post_type === 'portfolio') {
        $terms = get_the_terms($post->ID, 'portfolio_category');
        if ($terms && !is_wp_error($terms)) {
            $category = array_shift($terms);
            return str_replace('%portfolio_category%', $category->slug, $post_link);
        }
    }
    return $post_link;
}
add_filter('post_type_link', 'dprt_custom_permalinks', 10, 2);

// Register rewrite with taxonomy
register_post_type('portfolio', array(
    'rewrite' => array(
        'slug' => 'portfolio/%portfolio_category%',
        'with_front' => false
    ),
    // ... other args
));