Jetengine metabox: Dynamic number generator for CPT

gistfile1.txt

Description:
This custom PHP snippet adds functionality to WordPress and Jetengine metabox, automatically assigning and updating 
a sequence number for each post within a CPT. The sequence numbers are recalculated and updated dynamically whenever 
a post is added, deleted, or trashed, ensuring that the newest post receives the number 1 and other posts are numbered 
accordingly in descending order of their creation date. Additionally, the code implements a nonce for security, 
ensuring its validity, particularly when used in form submissions or similar contexts.

1. Copy the custom code and create a PHP snippet. Paste the code into your snippet plugin.
2. First, create a Custom Post Type (CPT). Change the CPT name from "rent-car" to your preferred CPT slug name. 
Search for "rent-car" in the custom code and replace all instances with your chosen CPT name.
3. Next, create a metabox and link it to your CPT.
4. Create a metafield and name it "generate-numbers.
5. Construct a listing grid and utilize dynamic fields. Set it to Meta data and locate "generate-numbers" as the source. 
You'll then see the result. Design your listing grid, add the products you desire, and save it. 
Use the listing grid widget to display the new listing grid.

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// Function to add a custom meta box for posts
function add_custom_meta_box() {
    add_meta_box(
        'generate_number_meta_box', 
        'Generate Number', 
        'display_number_meta_box', 
        'rent-car', // Post type where the meta box will be added (Change 'rent-car' to your custom post type)
        'normal', 
        'high' 
    );
}
add_action('add_meta_boxes', 'add_custom_meta_box');

// Callback function for displaying the meta box
function display_number_meta_box($post) {
    // Nonce field for security, unique action name for nonce
    wp_nonce_field('secure_action_generate_numbers', 'secure_nonce_generate_numbers');
    $number = get_post_meta($post->ID, 'generate-numbers', true);
    echo '<p>Post Number: ' . ($number ? $number : 'Number not set yet.') . '</p>';
}

// Function to update the generate number meta field for posts
function refresh_post_numbers() {
    $args = array(
        'post_type'      => 'rent-car', // Specify your custom post type here
        'post_status'    => 'publish',
        'posts_per_page' => -1,
        'orderby'        => 'date',
        'order'          => 'DESC'
    );
    $query = new WP_Query($args);
    $count = 1;

    if ($query->have_posts()) {
        while ($query->have_posts()) {
            $query->the_post();
            update_post_meta(get_the_ID(), 'generate-numbers', $count); 
            $count++;
        }
    }
    wp_reset_postdata();
}

// Ensure numbers are updated after a post is fully inserted into the database
add_action('wp_after_insert_post', 'handle_post_insert_update', 10, 3);

// Function called after a post is inserted or updated
function handle_post_insert_update($post_id, $post, $update) {
    if (!isset($_POST['secure_nonce_generate_numbers']) ||
        !wp_verify_nonce($_POST['secure_nonce_generate_numbers'], 'secure_action_generate_numbers')) {
        return;
    }
    if (wp_is_post_revision($post_id) || wp_is_post_autosave($post_id) ||
        'rent-car' !== get_post_type($post)) { // Check custom post type
        return;
    }
    if ('publish' === get_post_status($post_id)) {
        refresh_post_numbers();
    }
}

// Hooks to handle post deletion and trashing, ensuring immediate recalculations
add_action('deleted_post', 'handle_post_deletion');
add_action('trashed_post', 'handle_post_deletion');

// Function called when a post is deleted or trashed
function handle_post_deletion($post_id) {
    if ('rent-car' === get_post_type($post_id) && !wp_is_post_revision($post_id)) { // Check custom post type
        refresh_post_numbers();
    }
}