🗂️ Content Management Concepts

WordPress as a CMS

A content management system lets people create and manage content without touching code. WordPress grew from a blogging tool into one of the most capable CMSs on the web precisely because it does five things well:

• Separates content from presentation — writers write; themes decide how it looks.
• Organizes content meaningfully — categories, tags, and custom taxonomies.
• Supports many content types — posts, pages, and unlimited custom post types.
• Controls publishing workflows — drafts, scheduling, revisions, and user roles.
• Reuses content — archives, search, related content, shortcodes, and blocks.

💡 A useful analogy: WordPress is like a well-run library. Books (posts) are shelved by section (category) and cross-referenced in the index (tags). The library can add a whole new special collection (a custom post type) with its own catalogue rules (a custom taxonomy) whenever a new kind of material arrives.

The Unified Content Model

Nearly all WordPress content lives in one table, wp_posts, differentiated by the post_type column. Posts, pages, attachments, revisions, and your custom types are all "posts" under the hood.

Custom Post Types

Custom post types (CPTs) extend WordPress to model content it doesn't ship with. You register them with register_post_type(), hooked to init, usually from a plugin (so the content survives a theme switch).

<?php
add_action( 'init', 'mycb_register_project_cpt' );

function mycb_register_project_cpt(): void {
    $labels = [
        'name'          => _x( 'Projects', 'Post type general name', 'mycb' ),
        'singular_name' => _x( 'Project', 'Post type singular name', 'mycb' ),
        'menu_name'     => _x( 'Projects', 'Admin Menu text', 'mycb' ),
        'add_new_item'  => __( 'Add New Project', 'mycb' ),
        'edit_item'     => __( 'Edit Project', 'mycb' ),
        'all_items'     => __( 'All Projects', 'mycb' ),
        'not_found'     => __( 'No projects found.', 'mycb' ),
    ];

    $args = [
        'labels'       => $labels,
        'public'       => true,
        'has_archive'  => true,
        'hierarchical' => false,                          // like posts, not pages
        'menu_icon'    => 'dashicons-portfolio',
        'menu_position'=> 5,
        'rewrite'      => [ 'slug' => 'projects' ],
        'supports'     => [ 'title', 'editor', 'author', 'thumbnail', 'excerpt' ],
        'show_in_rest' => true,                           // enables the block editor + REST
    ];

    register_post_type( 'project', $args );
}

Taxonomies

Taxonomies classify content. WordPress ships two: categories (hierarchical) and tags (flat). You can register your own to organize custom post types.

Registering a custom taxonomy

<?php
add_action( 'init', 'mycb_register_skill_taxonomy' );

function mycb_register_skill_taxonomy(): void {
    $labels = [
        'name'          => _x( 'Skills', 'taxonomy general name', 'mycb' ),
        'singular_name' => _x( 'Skill', 'taxonomy singular name', 'mycb' ),
        'add_new_item'  => __( 'Add New Skill', 'mycb' ),
        'menu_name'     => __( 'Skills', 'mycb' ),
    ];

    $args = [
        'labels'            => $labels,
        'hierarchical'      => false,   // false = tag-like, true = category-like
        'public'            => true,
        'show_admin_column' => true,     // a handy column in the post list
        'rewrite'           => [ 'slug' => 'skills' ],
        'show_in_rest'      => true,
    ];

    // Attach the taxonomy to the 'project' post type.
    register_taxonomy( 'skill', [ 'project' ], $args );
}

Post Meta & Custom Fields

Post meta stores arbitrary key–value data alongside a post in wp_postmeta. It's how you attach a price to a product, a date to an event, or a client name to a project.

The four meta functions

<?php
add_post_meta( $post_id, '_project_client', 'Acme Co', true );   // add (unique)
$client = get_post_meta( $post_id, '_project_client', true );    // read single value
update_post_meta( $post_id, '_project_client', 'Globex' );       // update (or create)
delete_post_meta( $post_id, '_project_client' );                 // delete

A secure meta box

When you build your own editor UI for meta, three checks are non-negotiable on save: a valid nonce, not an autosave, and the user has permission.

<?php
// 1. Register the meta box.
add_action( 'add_meta_boxes', function (): void {
    add_meta_box( 'project_details', 'Project Details', 'mycb_render_box', 'project', 'normal', 'high' );
} );

// 2. Render it (with a nonce).
function mycb_render_box( WP_Post $post ): void {
    wp_nonce_field( 'project_details_save', 'project_details_nonce' );
    $client = get_post_meta( $post->ID, '_project_client', true );
    printf(
        '<p><label for="project_client">Client:</label>
         <input type="text" id="project_client" name="project_client" value="%s" class="widefat"></p>',
        esc_attr( $client )
    );
}

// 3. Save it — safely.
add_action( 'save_post_project', function ( int $post_id ): void {
    if ( ! isset( $_POST['project_details_nonce'] )
         || ! wp_verify_nonce( $_POST['project_details_nonce'], 'project_details_save' ) ) {
        return;
    }
    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
        return;
    }
    if ( ! current_user_can( 'edit_post', $post_id ) ) {
        return;
    }
    if ( isset( $_POST['project_client'] ) ) {
        update_post_meta( $post_id, '_project_client', sanitize_text_field( $_POST['project_client'] ) );
    }
} );

WP_Query & The Loop

WP_Query is the engine that fetches content; The Loop is the pattern that displays it. Together they render almost every page on a WordPress site.

A custom query and Loop

<?php
$recent = new WP_Query( [
    'post_type'      => 'post',
    'posts_per_page' => 5,
    'orderby'        => 'date',
    'order'          => 'DESC',
] );

if ( $recent->have_posts() ) :
    while ( $recent->have_posts() ) : $recent->the_post(); ?>
        <article>
            <h2><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>
            <p class="meta"><?php echo esc_html( get_the_date() ); ?> by <?php the_author(); ?></p>
            <div class="excerpt"><?php the_excerpt(); ?></div>
        </article>
    <?php endwhile;
    wp_reset_postdata();          // ALWAYS reset after a custom query
else :
    echo '<p>No posts found.</p>';
endif;

Filtering by taxonomy and meta

<?php
$featured_projects = new WP_Query( [
    'post_type'  => 'project',
    'tax_query'  => [
        [ 'taxonomy' => 'skill', 'field' => 'slug', 'terms' => [ 'javascript', 'php' ], 'operator' => 'AND' ],
    ],
    'meta_query' => [
        [ 'key' => '_featured', 'value' => '1', 'compare' => '=' ],
    ],
] );

Modify the main query with pre_get_posts

To change the main query (an archive, the blog page, search) don't build a new WP_Query — adjust the existing one before it runs. This is faster and preserves pagination.

<?php
add_action( 'pre_get_posts', function ( WP_Query $query ): void {
    // Guard: only the main, front-end query.
    if ( is_admin() || ! $query->is_main_query() ) {
        return;
    }
    // Show 20 posts on category archives instead of the default.
    if ( $query->is_category() ) {
        $query->set( 'posts_per_page', 20 );
    }
    // Include custom post types in search results.
    if ( $query->is_search() ) {
        $query->set( 'post_type', [ 'post', 'page', 'project' ] );
    }
} );

Media Management

Every uploaded file becomes an attachment post. The Media Library is your central store; in code, a small set of functions covers most needs.

Featured images and sizes

<?php
// Register custom sizes once (in the theme).
add_action( 'after_setup_theme', function (): void {
    add_theme_support( 'post-thumbnails' );
    add_image_size( 'project-card', 600, 400, true ); // width, height, hard crop
} );

// In a template:
if ( has_post_thumbnail() ) {
    the_post_thumbnail( 'project-card', [ 'class' => 'card-image' ] );
}

// Just the URL:
$url = get_the_post_thumbnail_url( get_the_ID(), 'full' );

Programmatic uploads (front-end forms)

<?php
function mycb_handle_upload(): int|WP_Error {
    if ( ! isset( $_POST['upload_nonce'] )
         || ! wp_verify_nonce( $_POST['upload_nonce'], 'mycb_upload' ) ) {
        return new WP_Error( 'nonce', 'Security check failed' );
    }
    if ( empty( $_FILES['my_file'] ) ) {
        return new WP_Error( 'no_file', 'No file uploaded' );
    }

    require_once ABSPATH . 'wp-admin/includes/file.php';
    require_once ABSPATH . 'wp-admin/includes/image.php';
    require_once ABSPATH . 'wp-admin/includes/media.php';

    // media_handle_upload validates type, moves the file, and creates the attachment.
    return media_handle_upload( 'my_file', 0 );
}

media_handle_upload() does the heavy lifting: it validates the MIME type against WordPress's allow-list, moves the file into uploads/, generates the sized thumbnails, and inserts the attachment post — returning the new attachment ID (or a WP_Error).

Hands-on: Recipe Architecture

<?php
add_action( 'init', function (): void {
    register_post_type( 'recipe', [
        'labels'       => [ 'name' => 'Recipes', 'singular_name' => 'Recipe' ],
        'public'       => true,
        'has_archive'  => true,
        'menu_icon'    => 'dashicons-food',
        'supports'     => [ 'title', 'editor', 'thumbnail', 'excerpt' ],
        'show_in_rest' => true,
        'rewrite'      => [ 'slug' => 'recipes' ],
    ] );

    register_taxonomy( 'meal_type', 'recipe', [ 'hierarchical' => true,  'show_in_rest' => true, 'label' => 'Meal Types' ] );
    register_taxonomy( 'cuisine',   'recipe', [ 'hierarchical' => true,  'show_in_rest' => true, 'label' => 'Cuisines' ] );
    register_taxonomy( 'dietary',   'recipe', [ 'hierarchical' => false, 'show_in_rest' => true, 'label' => 'Dietary' ] );
} );

// "Quick vegetarian dinners under 30 minutes"
$quick = new WP_Query( [
    'post_type'  => 'recipe',
    'tax_query'  => [
        [ 'taxonomy' => 'meal_type', 'field' => 'slug', 'terms' => 'dinner' ],
        [ 'taxonomy' => 'dietary',   'field' => 'slug', 'terms' => 'vegetarian' ],
    ],
    'meta_query' => [
        [ 'key' => '_prep_minutes', 'value' => 30, 'type' => 'NUMERIC', 'compare' => '<=' ],
    ],
] );

Best Practices

Summary & Quiz

📚 Further Reading

• Plugin Handbook — Custom Post Types
• Plugin Handbook — Taxonomies
• WP_Query Class Reference
• Advanced Custom Fields Documentation

🚀 What's Next?

You now know how WordPress structures content. Next we get it running: the installation options and configuration that turn a bare server into a working WordPress site.