WordPress Plugin Development

1my-plugin/
2├── my-plugin.php          # Main plugin file (REQUIRED)
3└── readme.txt             # Plugin documentation (recommended)

1my-plugin/
2├── my-plugin.php                  # Main plugin file with header
3├── uninstall.php                  # Uninstall cleanup (optional)
4├── readme.txt                     # WordPress.org readme
5├── LICENSE.txt                    # License file
6│
7├── includes/                      # Core plugin files
8│   ├── class-activator.php       # Activation logic
9│   ├── class-deactivator.php     # Deactivation logic
10│   ├── class-plugin.php          # Main plugin class
11│   └── class-loader.php          # Hooks loader
12│
13├── admin/                         # Admin-specific functionality
14│   ├── class-admin.php           # Admin hooks and functionality
15│   ├── partials/                 # Admin view templates
16│   │   └── admin-display.php
17│   ├── css/
18│   │   └── admin.css
19│   └── js/
20│       └── admin.js
21│
22├── public/                        # Public-facing functionality
23│   ├── class-public.php          # Public hooks and functionality
24│   ├── partials/                 # Public view templates
25│   │   └── public-display.php
26│   ├── css/
27│   │   └── public.css
28│   └── js/
29│       └── public.js
30│
31├── languages/                     # Translation files
32│   └── my-plugin.pot
33│
34└── assets/                        # Additional assets
35    ├── images/
36    ├── fonts/
37    └── icon-256x256.png          # Plugin icon

1<?php
2/**
3 * Plugin Name:       My Awesome Plugin
4 * Plugin URI:        https://example.com/my-awesome-plugin
5 * Description:       A comprehensive plugin that demonstrates best practices for WordPress plugin development.
6 * Version:           1.0.0
7 * Requires at least: 6.0
8 * Requires PHP:      8.0
9 * Author:            Your Name
10 * Author URI:        https://example.com
11 * License:           GPL v2 or later
12 * License URI:       https://www.gnu.org/licenses/gpl-2.0.html
13 * Text Domain:       my-awesome-plugin
14 * Domain Path:       /languages
15 * Update URI:        https://example.com/my-awesome-plugin/updates
16 */
17
18// Exit if accessed directly
19if (!defined('ABSPATH')) {
20    exit;
21}
22
23// Define plugin constants
24define('MY_PLUGIN_VERSION', '1.0.0');
25define('MY_PLUGIN_PATH', plugin_dir_path(__FILE__));
26define('MY_PLUGIN_URL', plugin_dir_url(__FILE__));
27define('MY_PLUGIN_BASENAME', plugin_basename(__FILE__));
28
29/**
30 * Plugin activation hook
31 */
32function my_plugin_activate() {
33    require_once MY_PLUGIN_PATH . 'includes/class-activator.php';
34    My_Plugin_Activator::activate();
35}
36register_activation_hook(__FILE__, 'my_plugin_activate');
37
38/**
39 * Plugin deactivation hook
40 */
41function my_plugin_deactivate() {
42    require_once MY_PLUGIN_PATH . 'includes/class-deactivator.php';
43    My_Plugin_Deactivator::deactivate();
44}
45register_deactivation_hook(__FILE__, 'my_plugin_deactivate');
46
47/**
48 * Initialize the plugin
49 */
50function my_plugin_init() {
51    require_once MY_PLUGIN_PATH . 'includes/class-plugin.php';
52    $plugin = new My_Plugin();
53    $plugin->run();
54}
55add_action('plugins_loaded', 'my_plugin_init');

1<?php
2/**
3 * Basic Action Example
4 * Hook: Execute code when WordPress initializes
5 */
6function my_plugin_init_function() {
7    // Your code here
8    error_log('My plugin initialized!');
9}
10add_action('init', 'my_plugin_init_function');
11
12/**
13 * Action with Priority and Arguments
14 * Hook: Execute code after a post is saved
15 *
16 * @param int     $post_id Post ID
17 * @param WP_Post $post    Post object
18 * @param bool    $update  Whether this is an update
19 */
20function my_plugin_save_post($post_id, $post, $update) {
21    // Skip autosaves
22    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
23        return;
24    }
25
26    // Check user permissions
27    if (!current_user_can('edit_post', $post_id)) {
28        return;
29    }
30
31    // Your custom logic
32    error_log("Post {$post_id} was saved!");
33
34    // Update custom meta
35    update_post_meta($post_id, '_last_modified_by', get_current_user_id());
36}
37// Priority 10 (default), accepts 3 arguments
38add_action('save_post', 'my_plugin_save_post', 10, 3);
39
40/**
41 * Custom Action Hook
42 * Create your own action hook for other plugins/themes to use
43 */
44function my_plugin_process_data($data) {
45    // Process the data
46    $processed_data = strtoupper($data);
47
48    // Fire custom action
49    do_action('my_plugin_data_processed', $processed_data, $data);
50
51    return $processed_data;
52}
53
54/**
55 * Another plugin/theme can hook into your custom action
56 */
57add_action('my_plugin_data_processed', function($processed, $original) {
58    error_log("Original: {$original}, Processed: {$processed}");
59}, 10, 2);

1<?php
2/**
3 * Basic Filter Example
4 * Modify the post content
5 */
6function my_plugin_modify_content($content) {
7    // Add signature to the end of post content
8    if (is_single()) {
9        $content .= '<p class="signature">Written by ' . get_the_author() . '</p>';
10    }
11    return $content; // IMPORTANT: Always return the content!
12}
13add_filter('the_content', 'my_plugin_modify_content');
14
15/**
16 * Filter with Priority and Arguments
17 * Modify the post title
18 */
19function my_plugin_modify_title($title, $post_id) {
20    // Add prefix to drafts
21    $post = get_post($post_id);
22    if ($post && $post->post_status === 'draft') {
23        $title = '[DRAFT] ' . $title;
24    }
25    return $title;
26}
27add_filter('the_title', 'my_plugin_modify_title', 10, 2);
28
29/**
30 * Custom Filter Hook
31 * Create your own filter for other plugins/themes to use
32 */
33function my_plugin_get_greeting($name) {
34    $greeting = "Hello, {$name}!";
35
36    // Apply custom filter
37    $greeting = apply_filters('my_plugin_greeting', $greeting, $name);
38
39    return $greeting;
40}
41
42/**
43 * Another plugin/theme can modify the greeting
44 */
45add_filter('my_plugin_greeting', function($greeting, $name) {
46    // Make it more formal
47    return "Good day, {$name}!";
48}, 10, 2);
49
50/**
51 * Conditional Filter
52 * Apply filter only in certain conditions
53 */
54function my_plugin_conditional_filter($content) {
55    // Only apply on posts, not pages
56    if (is_singular('post')) {
57        $content = '<div class="post-wrapper">' . $content . '</div>';
58    }
59    return $content;
60}
61add_filter('the_content', 'my_plugin_conditional_filter', 20);

1<?php
2/**
3 * Using $wpdb for database operations
4 */
5global $wpdb;
6
7/**
8 * SELECT Query - Get single row
9 */
10$user_id = 1;
11$user = $wpdb->get_row(
12    $wpdb->prepare(
13        "SELECT * FROM {$wpdb->users} WHERE ID = %d",
14        $user_id
15    )
16);
17
18if ($user) {
19    echo "User: " . $user->user_login;
20}
21
22/**
23 * SELECT Query - Get multiple rows
24 */
25$results = $wpdb->get_results(
26    "SELECT ID, post_title FROM {$wpdb->posts} WHERE post_status = 'publish' LIMIT 10"
27);
28
29foreach ($results as $post) {
30    echo $post->post_title . '<br>';
31}
32
33/**
34 * SELECT Query - Get single variable
35 */
36$post_count = $wpdb->get_var(
37    "SELECT COUNT(*) FROM {$wpdb->posts} WHERE post_status = 'publish'"
38);
39echo "Total published posts: {$post_count}";
40
41/**
42 * SELECT Query - Get single column
43 */
44$post_ids = $wpdb->get_col(
45    "SELECT ID FROM {$wpdb->posts} WHERE post_type = 'post' LIMIT 5"
46);
47// Result: array(1, 2, 3, 4, 5)
48
49/**
50 * INSERT Query
51 */
52$inserted = $wpdb->insert(
53    $wpdb->prefix . 'my_custom_table',
54    array(
55        'name'       => 'John Doe',
56        'email'      => '[email protected]',
57        'created_at' => current_time('mysql'),
58    ),
59    array('%s', '%s', '%s') // Data format: %s = string, %d = integer, %f = float
60);
61
62if ($inserted) {
63    $insert_id = $wpdb->insert_id;
64    echo "Inserted row ID: {$insert_id}";
65}
66
67/**
68 * UPDATE Query
69 */
70$updated = $wpdb->update(
71    $wpdb->prefix . 'my_custom_table',
72    array('name' => 'Jane Doe'),           // Data to update
73    array('ID' => 5),                       // WHERE clause
74    array('%s'),                            // Data format
75    array('%d')                             // WHERE format
76);
77
78echo "Rows updated: {$updated}";
79
80/**
81 * DELETE Query
82 */
83$deleted = $wpdb->delete(
84    $wpdb->prefix . 'my_custom_table',
85    array('ID' => 5),                       // WHERE clause
86    array('%d')                             // WHERE format
87);
88
89echo "Rows deleted: {$deleted}";
90
91/**
92 * Complex query with $wpdb->prepare() for security
93 */
94$post_type = 'post';
95$status = 'publish';
96$limit = 10;
97
98$results = $wpdb->get_results(
99    $wpdb->prepare(
100        "SELECT p.ID, p.post_title, pm.meta_value as views
101         FROM {$wpdb->posts} p
102         LEFT JOIN {$wpdb->postmeta} pm ON p.ID = pm.post_id AND pm.meta_key = 'post_views'
103         WHERE p.post_type = %s AND p.post_status = %s
104         ORDER BY CAST(pm.meta_value AS UNSIGNED) DESC
105         LIMIT %d",
106        $post_type,
107        $status,
108        $limit
109    )
110);

1<?php
2/**
3 * Create custom database table on plugin activation
4 */
5function my_plugin_create_tables() {
6    global $wpdb;
7
8    $table_name = $wpdb->prefix . 'my_custom_table';
9    $charset_collate = $wpdb->get_charset_collate();
10
11    $sql = "CREATE TABLE {$table_name} (
12        id bigint(20) UNSIGNED NOT NULL AUTO_INCREMENT,
13        user_id bigint(20) UNSIGNED NOT NULL,
14        name varchar(255) NOT NULL,
15        email varchar(255) NOT NULL,
16        status varchar(20) DEFAULT 'active',
17        metadata longtext,
18        created_at datetime NOT NULL,
19        updated_at datetime NOT NULL,
20        PRIMARY KEY  (id),
21        KEY user_id (user_id),
22        KEY status (status),
23        KEY created_at (created_at)
24    ) {$charset_collate};";
25
26    require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
27    dbDelta($sql);
28
29    // Store database version for future upgrades
30    add_option('my_plugin_db_version', '1.0');
31}
32register_activation_hook(__FILE__, 'my_plugin_create_tables');
33
34/**
35 * Database CRUD operations for custom table
36 */
37class My_Plugin_DB {
38
39    private $table_name;
40
41    public function __construct() {
42        global $wpdb;
43        $this->table_name = $wpdb->prefix . 'my_custom_table';
44    }
45
46    /**
47     * Create a new record
48     */
49    public function create($data) {
50        global $wpdb;
51
52        $defaults = array(
53            'user_id'    => get_current_user_id(),
54            'created_at' => current_time('mysql'),
55            'updated_at' => current_time('mysql'),
56        );
57
58        $data = wp_parse_args($data, $defaults);
59
60        $inserted = $wpdb->insert(
61            $this->table_name,
62            $data,
63            array('%d', '%s', '%s', '%s', '%s', '%s', '%s')
64        );
65
66        return $inserted ? $wpdb->insert_id : false;
67    }
68
69    /**
70     * Get a single record by ID
71     */
72    public function get($id) {
73        global $wpdb;
74
75        return $wpdb->get_row(
76            $wpdb->prepare(
77                "SELECT * FROM {$this->table_name} WHERE id = %d",
78                $id
79            )
80        );
81    }
82
83    /**
84     * Get all records with optional filters
85     */
86    public function get_all($args = array()) {
87        global $wpdb;
88
89        $defaults = array(
90            'status'   => 'active',
91            'user_id'  => 0,
92            'orderby'  => 'created_at',
93            'order'    => 'DESC',
94            'limit'    => 10,
95            'offset'   => 0,
96        );
97
98        $args = wp_parse_args($args, $defaults);
99
100        $where = array();
101        $where_values = array();
102
103        if ($args['status']) {
104            $where[] = 'status = %s';
105            $where_values[] = $args['status'];
106        }
107
108        if ($args['user_id']) {
109            $where[] = 'user_id = %d';
110            $where_values[] = $args['user_id'];
111        }
112
113        $where_clause = !empty($where) ? 'WHERE ' . implode(' AND ', $where) : '';
114
115        $query = "SELECT * FROM {$this->table_name} {$where_clause}
116                  ORDER BY {$args['orderby']} {$args['order']}
117                  LIMIT %d OFFSET %d";
118
119        $where_values[] = $args['limit'];
120        $where_values[] = $args['offset'];
121
122        return $wpdb->get_results(
123            $wpdb->prepare($query, $where_values)
124        );
125    }
126
127    /**
128     * Update a record
129     */
130    public function update($id, $data) {
131        global $wpdb;
132
133        $data['updated_at'] = current_time('mysql');
134
135        return $wpdb->update(
136            $this->table_name,
137            $data,
138            array('id' => $id),
139            array('%s', '%s', '%s', '%s', '%s'),
140            array('%d')
141        );
142    }
143
144    /**
145     * Delete a record
146     */
147    public function delete($id) {
148        global $wpdb;
149
150        return $wpdb->delete(
151            $this->table_name,
152            array('id' => $id),
153            array('%d')
154        );
155    }
156
157    /**
158     * Get total count
159     */
160    public function count($args = array()) {
161        global $wpdb;
162
163        $where = array();
164        $where_values = array();
165
166        if (!empty($args['status'])) {
167            $where[] = 'status = %s';
168            $where_values[] = $args['status'];
169        }
170
171        if (!empty($args['user_id'])) {
172            $where[] = 'user_id = %d';
173            $where_values[] = $args['user_id'];
174        }
175
176        $where_clause = !empty($where) ? 'WHERE ' . implode(' AND ', $where) : '';
177
178        $query = "SELECT COUNT(*) FROM {$this->table_name} {$where_clause}";
179
180        if (!empty($where_values)) {
181            return $wpdb->get_var($wpdb->prepare($query, $where_values));
182        }
183
184        return $wpdb->get_var($query);
185    }
186}

1<?php
2/**
3 * Add admin menu pages
4 */
5function my_plugin_admin_menu() {
6    // Add top-level menu page
7    add_menu_page(
8        'My Plugin Settings',           // Page title
9        'My Plugin',                    // Menu title
10        'manage_options',               // Capability required
11        'my-plugin-settings',           // Menu slug
12        'my_plugin_settings_page',      // Callback function
13        'dashicons-admin-generic',      // Icon (dashicon class or URL)
14        30                              // Position (after Comments)
15    );
16
17    // Add submenu page
18    add_submenu_page(
19        'my-plugin-settings',           // Parent slug
20        'Advanced Settings',            // Page title
21        'Advanced',                     // Menu title
22        'manage_options',               // Capability
23        'my-plugin-advanced',           // Menu slug
24        'my_plugin_advanced_page'       // Callback function
25    );
26
27    // Add settings page under Settings menu
28    add_options_page(
29        'My Plugin Options',            // Page title
30        'My Plugin',                    // Menu title
31        'manage_options',               // Capability
32        'my-plugin-options',            // Menu slug
33        'my_plugin_options_page'        // Callback function
34    );
35}
36add_action('admin_menu', 'my_plugin_admin_menu');
37
38/**
39 * Settings page callback
40 */
41function my_plugin_settings_page() {
42    // Check user capabilities
43    if (!current_user_can('manage_options')) {
44        wp_die(__('You do not have sufficient permissions to access this page.'));
45    }
46
47    ?>
48    <div class="wrap">
49        <h1><?php echo esc_html(get_admin_page_title()); ?></h1>
50
51        <form action="options.php" method="post">
52            <?php
53            // Output security fields
54            settings_fields('my_plugin_settings');
55
56            // Output setting sections and fields
57            do_settings_sections('my-plugin-settings');
58
59            // Output save button
60            submit_button('Save Settings');
61            ?>
62        </form>
63    </div>
64    <?php
65}

1<?php
2/**
3 * Register plugin settings
4 */
5function my_plugin_register_settings() {
6    // Register a new setting
7    register_setting(
8        'my_plugin_settings',           // Option group
9        'my_plugin_options',            // Option name
10        array(
11            'type'              => 'array',
12            'sanitize_callback' => 'my_plugin_sanitize_options',
13            'default'           => array(),
14        )
15    );
16
17    // Add a settings section
18    add_settings_section(
19        'my_plugin_general_section',    // Section ID
20        'General Settings',              // Title
21        'my_plugin_general_section_cb',  // Callback
22        'my-plugin-settings'             // Page slug
23    );
24
25    // Add settings fields
26    add_settings_field(
27        'enable_feature',                // Field ID
28        'Enable Feature',                // Title
29        'my_plugin_enable_field_cb',     // Callback
30        'my-plugin-settings',            // Page slug
31        'my_plugin_general_section',     // Section ID
32        array('label_for' => 'enable_feature')
33    );
34
35    add_settings_field(
36        'api_key',
37        'API Key',
38        'my_plugin_api_key_field_cb',
39        'my-plugin-settings',
40        'my_plugin_general_section',
41        array('label_for' => 'api_key')
42    );
43
44    add_settings_field(
45        'items_per_page',
46        'Items Per Page',
47        'my_plugin_items_per_page_field_cb',
48        'my-plugin-settings',
49        'my_plugin_general_section',
50        array('label_for' => 'items_per_page')
51    );
52}
53add_action('admin_init', 'my_plugin_register_settings');
54
55/**
56 * Section callback
57 */
58function my_plugin_general_section_cb($args) {
59    ?>
60    <p>Configure the general settings for the plugin.</p>
61    <?php
62}
63
64/**
65 * Field callbacks
66 */
67function my_plugin_enable_field_cb($args) {
68    $options = get_option('my_plugin_options', array());
69    $value = isset($options['enable_feature']) ? $options['enable_feature'] : false;
70    ?>
71    <input type="checkbox"
72           id="<?php echo esc_attr($args['label_for']); ?>"
73           name="my_plugin_options[enable_feature]"
74           value="1"
75           <?php checked($value, 1); ?>>
76    <label for="<?php echo esc_attr($args['label_for']); ?>">
77        Enable this awesome feature
78    </label>
79    <?php
80}
81
82function my_plugin_api_key_field_cb($args) {
83    $options = get_option('my_plugin_options', array());
84    $value = isset($options['api_key']) ? $options['api_key'] : '';
85    ?>
86    <input type="text"
87           id="<?php echo esc_attr($args['label_for']); ?>"
88           name="my_plugin_options[api_key]"
89           value="<?php echo esc_attr($value); ?>"
90           class="regular-text">
91    <p class="description">Enter your API key from the service provider.</p>
92    <?php
93}
94
95function my_plugin_items_per_page_field_cb($args) {
96    $options = get_option('my_plugin_options', array());
97    $value = isset($options['items_per_page']) ? $options['items_per_page'] : 10;
98    ?>
99    <input type="number"
100           id="<?php echo esc_attr($args['label_for']); ?>"
101           name="my_plugin_options[items_per_page]"
102           value="<?php echo esc_attr($value); ?>"
103           min="1"
104           max="100"
105           class="small-text">
106    <?php
107}
108
109/**
110 * Sanitize settings
111 */
112function my_plugin_sanitize_options($input) {
113    $sanitized = array();
114
115    if (isset($input['enable_feature'])) {
116        $sanitized['enable_feature'] = (bool) $input['enable_feature'];
117    }
118
119    if (isset($input['api_key'])) {
120        $sanitized['api_key'] = sanitize_text_field($input['api_key']);
121    }
122
123    if (isset($input['items_per_page'])) {
124        $sanitized['items_per_page'] = absint($input['items_per_page']);
125        if ($sanitized['items_per_page'] < 1) {
126            $sanitized['items_per_page'] = 10;
127        }
128    }
129
130    return $sanitized;
131}

1<?php
2/**
3 * Basic shortcode
4 * Usage: [hello_world]
5 */
6function my_plugin_hello_world_shortcode($atts) {
7    return '<p>Hello, World!</p>';
8}
9add_shortcode('hello_world', 'my_plugin_hello_world_shortcode');
10
11/**
12 * Shortcode with attributes
13 * Usage: [greeting name="John" time="morning"]
14 */
15function my_plugin_greeting_shortcode($atts) {
16    // Set default attributes
17    $atts = shortcode_atts(array(
18        'name' => 'Friend',
19        'time' => 'day',
20    ), $atts, 'greeting');
21
22    // Sanitize attributes
23    $name = sanitize_text_field($atts['name']);
24    $time = sanitize_text_field($atts['time']);
25
26    // Generate output
27    $greetings = array(
28        'morning'   => 'Good morning',
29        'afternoon' => 'Good afternoon',
30        'evening'   => 'Good evening',
31        'day'       => 'Good day',
32    );
33
34    $greeting = isset($greetings[$time]) ? $greetings[$time] : $greetings['day'];
35
36    return '<p class="greeting">' . esc_html($greeting . ', ' . $name) . '!</p>';
37}
38add_shortcode('greeting', 'my_plugin_greeting_shortcode');
39
40/**
41 * Shortcode with content
42 * Usage: [box color="blue"]Content here[/box]
43 */
44function my_plugin_box_shortcode($atts, $content = null) {
45    $atts = shortcode_atts(array(
46        'color' => 'gray',
47        'style' => 'default',
48    ), $atts, 'box');
49
50    $color = sanitize_html_class($atts['color']);
51    $style = sanitize_html_class($atts['style']);
52
53    $output = '<div class="my-plugin-box box-' . $color . ' box-style-' . $style . '">';
54    $output .= do_shortcode($content); // Allow nested shortcodes
55    $output .= '</div>';
56
57    return $output;
58}
59add_shortcode('box', 'my_plugin_box_shortcode');
60
61/**
62 * Complex shortcode with database query
63 * Usage: [recent_posts count="5" category="news"]
64 */
65function my_plugin_recent_posts_shortcode($atts) {
66    $atts = shortcode_atts(array(
67        'count'    => 5,
68        'category' => '',
69        'orderby'  => 'date',
70    ), $atts, 'recent_posts');
71
72    $args = array(
73        'posts_per_page' => absint($atts['count']),
74        'orderby'        => sanitize_text_field($atts['orderby']),
75        'order'          => 'DESC',
76    );
77
78    if (!empty($atts['category'])) {
79        $args['category_name'] = sanitize_text_field($atts['category']);
80    }
81
82    $query = new WP_Query($args);
83
84    // Start output buffering
85    ob_start();
86
87    if ($query->have_posts()) :
88        ?>
89        <div class="my-plugin-recent-posts">
90            <ul>
91                <?php while ($query->have_posts()) : $query->the_post(); ?>
92                    <li>
93                        <a href="<?php the_permalink(); ?>">
94                            <?php the_title(); ?>
95                        </a>
96                        <span class="date"><?php echo get_the_date(); ?></span>
97                    </li>
98                <?php endwhile; ?>
99            </ul>
100        </div>
101        <?php
102        wp_reset_postdata();
103    else :
104        ?>
105        <p>No posts found.</p>
106        <?php
107    endif;
108
109    // Return the buffered output
110    return ob_get_clean();
111}

1<?php
2/**
3 * Enqueue scripts with AJAX support
4 */
5function my_plugin_enqueue_ajax_scripts() {
6    wp_enqueue_script(
7        'my-plugin-ajax',
8        plugins_url('js/ajax.js', __FILE__),
9        array('jquery'),
10        '1.0.0',
11        true
12    );
13
14    // Localize script with AJAX URL and nonce
15    wp_localize_script('my-plugin-ajax', 'myPluginAjax', array(
16        'ajaxUrl' => admin_url('admin-ajax.php'),
17        'nonce'   => wp_create_nonce('my_plugin_ajax_nonce'),
18    ));
19}
20add_action('wp_enqueue_scripts', 'my_plugin_enqueue_ajax_scripts');
21
22/**
23 * AJAX handler for logged-in users
24 */
25function my_plugin_ajax_handler() {
26    // Verify nonce
27    check_ajax_referer('my_plugin_ajax_nonce', 'nonce');
28
29    // Check user permissions
30    if (!current_user_can('read')) {
31        wp_send_json_error(array(
32            'message' => 'Insufficient permissions',
33        ), 403);
34    }
35
36    // Get and sanitize input
37    $action_type = isset($_POST['action_type']) ? sanitize_text_field($_POST['action_type']) : '';
38    $item_id = isset($_POST['item_id']) ? absint($_POST['item_id']) : 0;
39
40    // Validate input
41    if (empty($action_type) || !$item_id) {
42        wp_send_json_error(array(
43            'message' => 'Invalid parameters',
44        ), 400);
45    }
46
47    // Process the request
48    switch ($action_type) {
49        case 'like':
50            $result = my_plugin_process_like($item_id);
51            break;
52
53        case 'save':
54            $result = my_plugin_process_save($item_id);
55            break;
56
57        default:
58            wp_send_json_error(array(
59                'message' => 'Unknown action type',
60            ), 400);
61    }
62
63    // Return success response
64    if ($result) {
65        wp_send_json_success(array(
66            'message' => 'Action completed successfully',
67            'data'    => $result,
68        ));
69    } else {
70        wp_send_json_error(array(
71            'message' => 'Action failed',
72        ), 500);
73    }
74}
75add_action('wp_ajax_my_plugin_action', 'my_plugin_ajax_handler');
76
77/**
78 * AJAX handler for non-logged-in users
79 */
80function my_plugin_ajax_public_handler() {
81    // Verify nonce
82    check_ajax_referer('my_plugin_ajax_nonce', 'nonce');
83
84    // Process public data
85    $data = isset($_POST['data']) ? sanitize_text_field($_POST['data']) : '';
86
87    wp_send_json_success(array(
88        'message' => 'Public action completed',
89        'data'    => $data,
90    ));
91}
92add_action('wp_ajax_nopriv_my_plugin_public_action', 'my_plugin_ajax_public_handler');

1// js/ajax.js
2
3jQuery(document).ready(function($) {
4    'use strict';
5
6    /**
7     * Handle button click
8     */
9    $('.my-plugin-like-btn').on('click', function(e) {
10        e.preventDefault();
11
12        var button = $(this);
13        var itemId = button.data('item-id');
14
15        // Disable button during request
16        button.prop('disabled', true);
17
18        $.ajax({
19            url: myPluginAjax.ajaxUrl,
20            type: 'POST',
21            data: {
22                action: 'my_plugin_action',
23                action_type: 'like',
24                item_id: itemId,
25                nonce: myPluginAjax.nonce
26            },
27            success: function(response) {
28                if (response.success) {
29                    button.text('Liked!');
30                    button.addClass('liked');
31
32                    // Update count
33                    var count = response.data.like_count || 0;
34                    button.siblings('.like-count').text(count);
35                } else {
36                    alert('Error: ' + response.data.message);
37                }
38            },
39            error: function(xhr, status, error) {
40                alert('AJAX error: ' + error);
41            },
42            complete: function() {
43                // Re-enable button
44                button.prop('disabled', false);
45            }
46        });
47    });
48});

1<?php
2/**
3 * Register custom REST API routes
4 */
5function my_plugin_register_rest_routes() {
6    // Register a GET endpoint
7    register_rest_route('my-plugin/v1', '/items', array(
8        'methods'             => 'GET',
9        'callback'            => 'my_plugin_get_items',
10        'permission_callback' => '__return_true', // Public endpoint
11    ));
12
13    // Register a GET endpoint with ID parameter
14    register_rest_route('my-plugin/v1', '/items/(?P<id>\\d+)', array(
15        'methods'             => 'GET',
16        'callback'            => 'my_plugin_get_item',
17        'permission_callback' => '__return_true',
18        'args'                => array(
19            'id' => array(
20                'validate_callback' => function($param) {
21                    return is_numeric($param);
22                },
23            ),
24        ),
25    ));
26
27    // Register a POST endpoint (requires authentication)
28    register_rest_route('my-plugin/v1', '/items', array(
29        'methods'             => 'POST',
30        'callback'            => 'my_plugin_create_item',
31        'permission_callback' => function() {
32            return current_user_can('edit_posts');
33        },
34        'args'                => array(
35            'title' => array(
36                'required'          => true,
37                'validate_callback' => function($param) {
38                    return is_string($param) && !empty($param);
39                },
40                'sanitize_callback' => 'sanitize_text_field',
41            ),
42            'content' => array(
43                'required'          => true,
44                'sanitize_callback' => 'sanitize_textarea_field',
45            ),
46        ),
47    ));
48
49    // Register a DELETE endpoint
50    register_rest_route('my-plugin/v1', '/items/(?P<id>\\d+)', array(
51        'methods'             => 'DELETE',
52        'callback'            => 'my_plugin_delete_item',
53        'permission_callback' => function() {
54            return current_user_can('delete_posts');
55        },
56        'args'                => array(
57            'id' => array(
58                'validate_callback' => function($param) {
59                    return is_numeric($param);
60                },
61            ),
62        ),
63    ));
64}
65add_action('rest_api_init', 'my_plugin_register_rest_routes');
66
67/**
68 * REST API callbacks
69 */
70function my_plugin_get_items(WP_REST_Request $request) {
71    // Get query parameters
72    $per_page = $request->get_param('per_page') ?: 10;
73    $page = $request->get_param('page') ?: 1;
74
75    $db = new My_Plugin_DB();
76    $items = $db->get_all(array(
77        'limit'  => absint($per_page),
78        'offset' => absint(($page - 1) * $per_page),
79    ));
80
81    $total = $db->count();
82
83    $response = new WP_REST_Response($items);
84    $response->header('X-Total-Count', $total);
85    $response->header('X-Total-Pages', ceil($total / $per_page));
86
87    return $response;
88}
89
90function my_plugin_get_item(WP_REST_Request $request) {
91    $id = $request->get_param('id');
92    $db = new My_Plugin_DB();
93    $item = $db->get($id);
94
95    if (!$item) {
96        return new WP_Error(
97            'not_found',
98            'Item not found',
99            array('status' => 404)
100        );
101    }
102
103    return new WP_REST_Response($item, 200);
104}
105
106function my_plugin_create_item(WP_REST_Request $request) {
107    $db = new My_Plugin_DB();
108
109    $data = array(
110        'name'    => $request->get_param('title'),
111        'email'   => $request->get_param('content'),
112        'user_id' => get_current_user_id(),
113    );
114
115    $id = $db->create($data);
116
117    if (!$id) {
118        return new WP_Error(
119            'creation_failed',
120            'Failed to create item',
121            array('status' => 500)
122        );
123    }
124
125    $item = $db->get($id);
126
127    return new WP_REST_Response($item, 201);
128}
129
130function my_plugin_delete_item(WP_REST_Request $request) {
131    $id = $request->get_param('id');
132    $db = new My_Plugin_DB();
133
134    $deleted = $db->delete($id);
135
136    if (!$deleted) {
137        return new WP_Error(
138            'deletion_failed',
139            'Failed to delete item',
140            array('status' => 500)
141        );
142    }
143
144    return new WP_REST_Response(array(
145        'deleted' => true,
146        'id'      => $id,
147    ), 200);
148}