How to add custom supports for custom post types?

Question

I need to define a custom support feature for my WordPress Plugin but I can't find how to do so.

What I want to do is to display a box on certain custom post type containing 2 meta fields in which users can type in Longitude and Latitudes values for geolocalisation purposes.

For practical uses, i want to attach this custom feature the same way as supports are to posts :

<?php
$args = array(
    ...
    ...
    'supports' => array('title','editor', 'thumbnail', 'my_custom_support'),
    ...
    ...
);
register_post_type('my_custom_post_type', $args);
?>

OR, if my custom post type has already been created beforehand:

<?php
add_post_type_support('my_custom_post_type', 'my_custom_support');
?>

I know what I want but I just can't find how to register new supports ...

I hope someone can answer this problem because I'm actually tearing off my hairs!

Answer 1

Well you can add

...
'supports' => array('title','editor', 'thumbnail', 'custom-fields'),
...

You don't need to create anything beforehand, you can define the two fields latitude and longitude when adding a new post.

Answer 2

To add custom supports for custom post types in WordPress, you will need to use the add_post_type_support() function.

add_action('init', 'register_custom_post_type_support');

function register_custom_post_type_support() {
    add_post_type_support('my_custom_post_type', 'my_custom_support');
}

After adding support for the custom feature, you need to define the metabox containing the longitude and latitude fields. You can use the add_meta_box() function to add a metabox to your custom post type edit screen.

add_action('add_meta_boxes', 'add_custom_metabox');

function add_custom_metabox() {
    add_meta_box(
        'custom_geolocation_metabox',
        'Geolocation',
        'render_custom_geolocation_metabox',
        'my_custom_post_type',
        'normal',
        'default'
    );
}

function render_custom_geolocation_metabox($post) {
    // Retrieve longitude and latitude values
    $longitude = get_post_meta($post->ID, 'longitude', true);
    $latitude = get_post_meta($post->ID, 'latitude', true);
    ?>
    <label for="longitude">Longitude:</label>
    <input type="text" id="longitude" name="longitude" value="<?php echo esc_attr($longitude); ?>"><br>
    <label for="latitude">Latitude:</label>
    <input type="text" id="latitude" name="latitude" value="<?php echo esc_attr($latitude); ?>">
    <?php
}

add_action('save_post', 'save_custom_geolocation');

function save_custom_geolocation($post_id) {
    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return;

    // Save longitude and latitude values
    if (isset($_POST['longitude'])) {
        update_post_meta($post_id, 'longitude', sanitize_text_field($_POST['longitude']));
    }
    if (isset($_POST['latitude'])) {
        update_post_meta($post_id, 'latitude', sanitize_text_field($_POST['latitude']));
    }
}

In the code above, replace my_custom_post_type with the name of your custom post type, and my_custom_support with the name of the custom support feature you want to add.