uninstall.php

<?php
/**
 * Runs on Uninstall of SLM Plus
 *
 * @package   SLM Plus
 * @author    Michel Velis
 * @license   GPL-2.0+
 * @link      http://epikly.com
 */

// Exit if accessed directly
if (!defined('WP_UNINSTALL_PLUGIN')) {
    exit();
}

// Check user permissions
if (!current_user_can('activate_plugins')) {
    return;
}

global $wpdb;

// Delete all related options
$slm_options = array(
    'slm_db_version',
    'slm_plugin_options',
    'slm_lic_creation_secret',
    'slm_backup_dir_hash',
    'slm_woo_affect_downloads',
    'slm_woo_enable_my_licenses_page',
);

foreach ($slm_options as $option) {
    delete_option($option);
}

// List all tables related to the plugin
$tables_to_drop = array(
    $wpdb->prefix . 'lic_key_tbl',
    $wpdb->prefix . 'lic_reg_domain_tbl',
    $wpdb->prefix . 'lic_reg_devices_tbl',
    $wpdb->prefix . 'lic_log_tbl',
    $wpdb->prefix . 'slm_license_status',
    $wpdb->prefix . 'slm_subscribers_tbl',
    $wpdb->prefix . 'slm_activations_tbl',
);

// Drop custom database tables using the `prepare` method
foreach ($tables_to_drop as $table) {
    // Check if the table exists before attempting to drop it
    if ($wpdb->get_var($wpdb->prepare("SHOW TABLES LIKE %s", $table)) !== null) {
        // Drop the table if it exists
        $wpdb->query("DROP TABLE IF EXISTS {$table}");
    }
}

// Delete Custom Post Type posts and related metadata using the `delete` method
$post_types = array('slm_manage_license', 'slm_license_product'); // Add any other custom post types if needed
foreach ($post_types as $post_type) {
    // Check if post type data is cached
    $cached_posts = wp_cache_get($post_type, 'slm_posts');
    if ($cached_posts) {
        wp_cache_delete($post_type, 'slm_posts');
    }

    // Safely delete posts and metadata for this post type
    $wpdb->delete($wpdb->posts, array('post_type' => $post_type));
    $wpdb->delete($wpdb->postmeta, array('post_id' => $post_type));
}

// Clean orphaned postmeta entries using `DELETE` queries
$wpdb->query(
    "DELETE pm FROM {$wpdb->postmeta} pm
    LEFT JOIN {$wpdb->posts} p ON pm.post_id = p.ID
    WHERE p.ID IS NULL"
);

// Clean orphaned term relationships if there are custom taxonomies involved
$wpdb->query(
    "DELETE tr FROM {$wpdb->term_relationships} tr
    LEFT JOIN {$wpdb->posts} p ON tr.object_id = p.ID
    WHERE p.ID IS NULL"
);

// Delete custom user meta related to the plugin (if applicable)
$user_meta_keys = array(
    'slm_user_license_data',
    // Add any other related user meta keys here
);

foreach ($user_meta_keys as $meta_key) {
    // Check if user meta data is cached
    $cached_meta = wp_cache_get($meta_key, 'slm_usermeta');
    if ($cached_meta) {
        wp_cache_delete($meta_key, 'slm_usermeta');
    }

    $wpdb->delete($wpdb->usermeta, array('meta_key' => $meta_key));
}

// Clear the relevant cache after heavy operations
wp_cache_flush();