WordPress Plugin Skeleton

a.md

WordPress Plugin Skeleton

This plugin demonstrates how to:

• Wrap plugin code in PHP class
• Run code when plugin is activated, deactivated, and uninstalled
• Register custom post type with labels, menu icon, Gutenberg, and featured thumbnail
• Add custom admin columns and populate them with data
• Add new meta box, render custom fields, and save custom field values in database
• Register new settings, add new section to existing settings page, and sanitize values
• Display posts from custom post type at end of blog post

It accomplishes this with the following functions:

• register_activation_hook()
• register_deactivation_hook()
• register_uninstall_hook()
• add_action()
• add_filter()
• register_post_type()
• add_meta_box()
• get_post_meta()
• update_post_meta()
• add_settings_section()
• register_setting()
• add_settings_field()
• add_settings_error()
• esc_html()
• sanitize_text_field()
• get_option()
• get_posts()
• get_the_post_thumbnail()
• get_permalink()

And the following actions/filters:

• init
• manage_edit-movie_columns
• manage_movie_posts_custom_column
• add_meta_boxes
• save_post
• admin_init
• the_content

plugin.php

<?php

/**
 * Plugin Name: Movies
 * Description: Add movies to WordPress and feature them at the end a post.
 * Version: 1.0
 * Author: Ryan Sechrest
 * Author URI: https://ryansechrest.com/
 */

namespace RyanSechrest\Plugin\Movies;

use WP_Post;

class Main
{
    /**
     * Prefix
     *
     * Use prefix with IDs and database keys to prevent collisions.
     */
    const PREFIX = 'rsm';

    /************************************************************************************/

    /**
     * Register plugin components
     */
    public function __construct()
    {
        $this->register_main_plugin_hooks();
        $this->register_movie_post_type();
        $this->register_movie_admin_columns();
        $this->register_movie_details_meta_box();
        $this->register_movie_admin_settings();
        $this->register_movie_display();
    }

    /**
     * Initialize plugin
     *
     * @return Main
     */
    public static function init(): Main
    {
        return new Main();
    }

    /************************************************************************************/

    /**
     * Get option name with plugin prefix
     *
     * @param string $name
     * @return string
     */
    private function db_prefix(string $name): string
    {
        return $this->prefix($name, '_');
    }

    /**
     * Get HTML ID with plugin prefix
     *
     * @param string $id
     * @return string
     */
    private function id_prefix(string $id): string
    {
        return $this->prefix($id, '-');
    }

    /**
     * Get key with plugin prefix
     *
     * @param string $key
     * @param string $separator
     * @return string
     */
    private function prefix(string $key, string $separator): string
    {
        return $this::PREFIX . $separator . $key;
    }

    /************************************************************************************/

    /**
     * Register main plugin hooks
     *
     * @uses register_activation_hook()
     * @uses register_deactivation_hook()
     * @uses register_uninstall_hook()
     * @return void
     */
    private function register_main_plugin_hooks(): void
    {
        register_activation_hook(__FILE__, [$this, 'run_when_activated']);
        register_deactivation_hook(__FILE__, [$this, 'run_when_deactivated']);
        register_uninstall_hook(__FILE__, ['RyanSechrest\Plugin\Movies\Main', 'run_when_uninstalled']);
    }

    /*----------------------------------------------------------------------------------*/

    /**
     * Run when plugin is activated
     *
     * @return void
     */
    public function run_when_activated(): void
    {
        // ...
    }

    /**
     * Run when plugin is deactivated
     *
     * @return void
     */
    public function run_when_deactivated(): void
    {
        // ...
    }

    /**
     * Run when plugin is uninstalled
     *
     * @return void
     */
    public static function run_when_uninstalled(): void
    {
        delete_option(self::PREFIX . '_movie_display_total');
        delete_option(self::PREFIX . '_movie_display_enabled');
    }

    /************************************************************************************/

    /**
     * Register movie post type
     *
     * @uses add_action()
     * @return void
     */
    private function register_movie_post_type(): void
    {
        add_action(
            'init',
            [$this, 'hook__register_movie_post_type']
        );
    }

    /*----------------------------------------------------------------------------------*/

    /**
     * Hook: Register movie post type
     *
     * @uses register_post_type()
     * @return void
     */
    public function hook__register_movie_post_type(): void
    {
        register_post_type('movie',
            [
                'labels' => [
                    'name' => __('Movies', 'movies'),
                    'singular_name' => __('Movie', 'movies'),
                    'add_new' => __('Add Movie', 'movies'),
                    'add_new_item' => __('Add New Movie', 'movies'),
                    'edit_item' => __('Edit Movie', 'movies'),
                    'new_item' => __('New Movie', 'movies'),
                    'view_item' => __('View Movie', 'movies'),
                    'search_items' => __('Search Movies', 'movies'),
                    'not_found' => __('No movies found', 'movies'),
                    'not_found_in_trash' => __('No movies found in trash', 'movies'),

                ],
                'menu_icon' => 'dashicons-editor-video',
                'public' => true,
                'show_in_rest' => true,
                'supports' => ['title', 'editor', 'thumbnail'],
            ]
        );
    }

    /************************************************************************************/

    /**
     * Register movie admin columns
     *
     * @uses add_filter()
     * @uses add_action()
     * @return void
     */
    private function register_movie_admin_columns(): void
    {
        add_filter(
            'manage_edit-movie_columns',
            [$this, 'hook__add_movie_admin_columns']
        );
        add_action(
            'manage_movie_posts_custom_column',
            [$this, 'hook__render_movie_admin_column'],
            10,
            2
        );
    }

    /*----------------------------------------------------------------------------------*/

    /**
     * Hook: Add movie admin columns
     *
     * @param array $columns
     * @return array
     */
    public function hook__add_movie_admin_columns(array $columns): array
    {
        $new_columns = [];
        foreach ($columns as $index => $column) {
            $new_columns[$index] = $column;
            if ($column === 'Title') {
                $new_columns['director'] = __('Director', 'movies');
                $new_columns['producer'] = __('Producer', 'movies');
            }
        }

        return $new_columns;
    }

    /**
     * Hook: Render movie admin column
     *
     * @param string $column
     * @param int $id
     * @return void
     */
    public function hook__render_movie_admin_column(string $column, int $id): void
    {
        if (!$value = get_post_meta($id, $column, true)) {
            return;
        }

        echo $value;
    }

    /************************************************************************************/

    /**
     * Register movie details meta box
     *
     * @uses add_action()
     * @return void
     */
    private function register_movie_details_meta_box(): void
    {
        add_action(
            'add_meta_boxes',
            [$this, 'hook__add_movie_details_meta_box']
        );
        add_action(
            'save_post',
            [$this, 'hook__save_movie_details_fields']
        );
    }

    /*----------------------------------------------------------------------------------*/

    /**
     * Hook: Add movie details meta box
     *
     * @uses add_meta_box()
     * @return void
     */
    public function hook__add_movie_details_meta_box(): void
    {
        add_meta_box(
            $this->id_prefix('movie-details'),
            __('Details', 'movies'),
            [$this, 'hook__render_movie_details_fields'],
            'movie',
            'side'
        );
    }

    /**
     * Hook: Render movie details fields
     *
     * @uses get_post_meta()
     * @param WP_Post $post
     * @return void
     */
    public function hook__render_movie_details_fields(WP_Post $post): void
    {
        $director = get_post_meta($post->ID, 'director', true) ?: '';
        $producer = get_post_meta($post->ID, 'producer', true) ?: '';

        $output = '<div class="components-base-control__field" style="margin-bottom:15px;">';
        $output .= '<label for="director" class="components-base-control__label css-uc0dzf">Director</label>';
        $output .= '<input type="text" name="director" value="' . $director . '" id="director" class="components-text-control__input">';
        $output .= '</div>';

        $output .= '<div class="components-base-control__field">';
        $output .= '<label for="producer" class="components-base-control__label css-uc0dzf">Producer</label>';
        $output .= '<input type="text" name="producer" value="' . $producer . '" id="producer" class="components-text-control__input">';
        $output .= '</div>';

        echo $output;
    }

    /**
     * Hook: Save movie details fields
     *
     * @uses sanitize_text_field()
     * @uses update_post_meta()
     * @param int $post_id
     * @return void
     */
    public function hook__save_movie_details_fields(int $post_id): void
    {
        if (isset($_POST['director'])) {
            update_post_meta(
                $post_id,
                'director',
                sanitize_text_field($_POST['director'])
            );
        }
        if (isset($_POST['producer'])) {
            update_post_meta(
                $post_id,
                'producer',
                sanitize_text_field($_POST['producer'])
            );
        }
    }

    /************************************************************************************/

    /**
     * Register movie admin settings
     *
     * @uses add_action()
     * @return void
     */
    private function register_movie_admin_settings(): void
    {
        add_action('admin_init', [$this, 'hook__register_movie_admin_section']);
        add_action('admin_init', [$this, 'hook__register_movie_admin_settings']);
    }

    /*----------------------------------------------------------------------------------*/

    /**
     * Hook: Register movie admin section
     *
     * @uses add_settings_section()
     * @return void
     */
    public function hook__register_movie_admin_section(): void
    {
        add_settings_section(
            $this->id_prefix('movies-section'),
            'Movies',
            function() {
                echo '<p>Preferences to enable and customize the Movies plugin.</p>';
            },
            'reading'
        );
    }

    /**
     * Hook: Register movie admin settings
     *
     * @return void
     */
    public function hook__register_movie_admin_settings(): void
    {
        $this->register_movie_display_enabled_field();
        $this->register_movie_display_total_field();
    }

    /*----------------------------------------------------------------------------------*/

    /**
     * Register movie display enabled field
     *
     * @uses register_setting()
     * @uses add_settings_field()
     * @return void
     */
    private function register_movie_display_enabled_field(): void
    {
        register_setting(
            'reading',
            $this->db_prefix('movie_display_enabled'),
            [
                'type' => 'string',
                'sanitize_callback' => [$this, 'hook__sanitize_movie_display_enabled_field'],
                'default' => 'no',
            ]
        );
        add_settings_field(
            $this->id_prefix('movie-display-enabled-field'),
            'Display movies',
            [$this, 'hook__render_movie_display_enabled_field'],
            'reading',
            $this->id_prefix('movies-section')
        );
    }

    /**
     * Hook: Sanitize movie display enabled field
     *
     * @uses add_settings_error()
     * @param string $value
     * @return string
     */
    public function hook__sanitize_movie_display_enabled_field(string $value): string
    {
        $valid_values = ['yes', 'no'];
        if (!in_array($value, $valid_values)) {
            add_settings_error(
                'reading',
                'movie',
                __('Movies: Display movies was set to an invalid value. Using default: Nowhere', 'movies')
            );
            return 'no';
        }

        return $value;
    }

    /**
     * Hook: Render movie display enabled field
     *
     * @uses esc_html()
     * @uses get_option()
     * @return void
     */
    public function hook__render_movie_display_enabled_field(): void
    {
        $option_name = esc_html($this->db_prefix('movie_display_enabled'));
        $value = esc_html(get_option($option_name));

        // Start Wrapper
        $output = '<fieldset>';
        $output .= '<p>';

        // Option 1
        $output .= '<label>';
        $output .= '<input name="' . $option_name . '" type="radio" value="no" ';
        if ($value === 'no') {
            $output .= 'checked="checked"';
        }
        $output .= '>';
        $output .= ' Nowhere</label>';

        // New Line
        $output .= '<br>';

        // Option 2
        $output .= '<label>';
        $output .= '<input name="' . $option_name . '" type="radio" value="yes" ';
        if ($value === 'yes') {
            $output .= 'checked="checked"';
        }
        $output .= '>';
        $output .= ' After a blog post';
        $output .= '</label>';

        // End Wrapper
        $output .= '</p>';
        $output .= '</fieldset>';

        echo $output;
    }

    /*----------------------------------------------------------------------------------*/

    /**
     * Register movie display total field
     *
     * @uses register_setting()
     * @uses add_settings_field()
     * @return void
     */
    private function register_movie_display_total_field(): void
    {
        register_setting(
            'reading',
            $this->db_prefix('movie_display_total'),
            [
                'type' => 'integer',
                'sanitize_callback' => [$this, 'hook__sanitize_movie_display_total_field'],
                'default' => 1,
            ]
        );
        add_settings_field(
            $this->id_prefix('movie-display-total-field'),
            'Display up to',
            [$this, 'hook__render_movie_display_total_field'],
            'reading',
            $this->id_prefix('movies-section')
        );
    }

    /**
     * Hook: Sanitize movie display total field
     *
     * @uses add_settings_error()
     * @param string $value
     * @return string
     */
    public function hook__sanitize_movie_display_total_field(string $value): string
    {
        $value = (int) $value;
        if ($value < 1 || $value > 5) {
            add_settings_error(
                'reading',
                'movie',
                __('Movies: Display up to must be between 1-5. Using default: 1', 'movies')
            );
            return 1;
        }

        return $value;
    }

    /**
     * Hook: Render movie display total field
     *
     * @uses esc_html()
     * @uses get_option()
     * @return void
     */
    public function hook__render_movie_display_total_field(): void
    {
        $option_name = esc_html($this->db_prefix('movie_display_total'));
        $value = esc_html(get_option($option_name));

        $output = '<fieldset>';
        $output .= '<p>';
        $output .= '<input name="' . $option_name . '" type="number" value="';
        $output .= $value;
        $output .= '" step="1" min="1" max="5" id="movie-display-total" class="small-text"> movie(s)';
        $output .= '</p>';
        $output .= '</fieldset>';

        echo $output;
    }

    /************************************************************************************/

    /**
     * Register movie display
     *
     * @uses add_filter()
     * @return void
     */
    private function register_movie_display(): void
    {
        add_filter('the_content', [$this, 'hook__render_movies_end_of_post']);
    }

    /*----------------------------------------------------------------------------------*/

    /**
     * Hook: Render movies end of post
     *
     * @uses get_option()
     * @uses get_permalink()
     * @uses get_posts()
     * @uses get_the_post_thumbnail()
     * @param string $content
     * @return string
     */
    public function hook__render_movies_end_of_post(string $content): string
    {
        $enabled = get_option($this->db_prefix('movie_display_enabled'));
        if ($enabled !== 'yes') {
            return $content;
        }
        $total = get_option($this->db_prefix('movie_display_total'));
        $movies = get_posts([
            'post_type' => 'movie',
            'post_status' => 'publish',
            'posts_per_page' => $total,
            'orderby' => 'date',
            'order' => 'DESC',
        ]);
        if (count($movies) === 0) {
            return $content;
        }
        $content .= '<p>Here are our latest movies:</p>';
        $content .= '<div style="display:flex;gap:15px;">';
        /** @var WP_Post $movie */
        foreach ($movies as $movie) {
            $thumbnail = get_the_post_thumbnail($movie, [200, 300]);
            $url = get_permalink($movie);
            $content .= '<div>';
            $content .= '<div><a href="' . $url . '">' . $thumbnail . '</a></div>';
            $content .= '<div><a href="' . $url . '">' . $movie->post_title . '</a></div>';
            $content .= '</div>';
        }
        $content .= '</div>';

        return $content;
    }
}

Main::init();