Start documenting some of the callbacks.

src/register_meta.php

@@ -55,7 +55,12 @@ class register_meta extends Shared\Base {
 	public $default;
 
 	/**
-	 * A function or method to call when sanitizing `$meta_key` data.
+	 * A function or method to call when sanitizing the meta value.
+	 *
+	 * The callback is called via one of:
+	 *
+	 * - The https://developer.wordpress.org/reference/hooks/sanitize_object_type_meta_meta_key_for_object_subtype/ filter
+	 * - The https://developer.wordpress.org/reference/hooks/sanitize_object_type_meta_meta_key/ filter
 	 *
 	 * @var callable
 	 * @phpstan-var (callable(mixed,string,string,string): mixed)|(callable(mixed,string,string): mixed)
@@ -65,6 +70,11 @@ class register_meta extends Shared\Base {
 	/**
 	 * A function or method to call when performing `edit_post_meta`, `add_post_meta`, and `delete_post_meta` capability checks.
 	 *
+	 * The callback is called via one of:
+	 *
+	 * - The https://developer.wordpress.org/reference/hooks/auth_object_type_meta_meta_key_for_object_subtype/ filter
+	 * - The https://developer.wordpress.org/reference/hooks/auth_object_type_meta_meta_key/ filter
+	 *
 	 * @var callable
 	 * @phpstan-var (callable(bool,string,string,string): bool)|(callable(bool,string,string): bool)
 	 */
@@ -75,6 +85,8 @@ class register_meta extends Shared\Base {
 	 *
 	 * A custom post type must also declare support for custom fields for registered meta to be accessible via REST. When registering complex meta values this argument may optionally be an array with 'schema' or 'prepare_callback' keys instead of a boolean.
 	 *
+	 * If this value is an array with a prepare_callback key, the callback is called here: https://github.com/WordPress/wordpress-develop/blob/6.6.0/src/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php#L127
+	 *
 	 * @var bool|array<string, mixed>
 	 * @phpstan-var bool|array{
 	 *     schema: array<string,mixed>,

src/register_post_type.php

@@ -261,7 +261,7 @@ class register_post_type extends Shared\Base {
 	 *
 	 * Do `remove_meta_box()` and `add_meta_box()` calls in the callback.
 	 *
-	 * Default null.
+	 * The callback is called via the https://developer.wordpress.org/reference/hooks/add_meta_boxes_post_type/ action.
 	 *
 	 * @var callable
 	 * @phpstan-var callable(\WP_Post): void

src/register_rest_field.php

@@ -15,8 +15,10 @@ class register_rest_field extends Shared\Base {
 	 *
 	 * Default is 'null', the field will not be returned in the response. The function will be passed the prepared object data.
 	 *
+	 * The callback is called here: https://github.com/WordPress/wordpress-develop/blob/6.6.0/src/wp-includes/rest-api/endpoints/class-wp-rest-controller.php#L434-L440
+	 *
 	 * @var callable
-	 * @phpstan-var callable(mixed[],string,\WP_REST_Request): mixed
+	 * @phpstan-var callable(mixed[],string,\WP_REST_Request,string): mixed
 	 */
 	public $get_callback;
 
@@ -25,6 +27,8 @@ class register_rest_field extends Shared\Base {
 	 *
 	 * Default is 'null', the value cannot be set or updated. The function will be passed the model object, like `WP_Post`.
 	 *
+	 * The callback is called here: https://github.com/WordPress/wordpress-develop/blob/6.6.0/src/wp-includes/rest-api/endpoints/class-wp-rest-controller.php#L468-L475
+	 *
 	 * @var callable
 	 * @phpstan-var callable(mixed,object,string,\WP_REST_Request,string): mixed
 	 */

src/register_setting.php

@@ -37,6 +37,8 @@ class register_setting extends Shared\Base {
 	/**
 	 * A callback function that sanitizes the option's value.
 	 *
+	 * The callback is called via the https://developer.wordpress.org/reference/hooks/sanitize_option_option/ filter.
+	 *
 	 * @var callable
 	 * @phpstan-var callable(mixed,string,mixed):mixed
 	 */

src/register_taxonomy.php

@@ -106,6 +106,8 @@ class register_taxonomy extends Shared\Base {
 	/**
 	 * Provide a callback function for the meta box display. If not set, `post_categories_meta_box()` is used for hierarchical taxonomies, and `post_tags_meta_box()` is used for non-hierarchical. If false, no meta box is shown.
 	 *
+	 * The callback is called in `do_meta_boxes()`: https://github.com/WordPress/wordpress-develop/blob/6.6.0/src/wp-admin/includes/template.php#L1456
+	 *
 	 * @var false|callable
 	 * @phpstan-var false|callable(\WP_Post,mixed[]): void
 	 */