put Xprofile fields into a Group (BuddyPress)

my-plugin.php

<?php
// Increment used to store xprofile data for a user ID that's unlikely to exist.
const GROUP_USER_ID_INCREMENT = 1000000;

/**
 * Add xprofile profile fields to a BuddyPress Group.
 */
class Groups_Extension_Profile_Fields extends \BP_Group_Extension
{

	/**
	 * Group_Extension_Profile_Fields constructor.
	 *
	 * Initializes the group extension with specific arguments.
	 */
	public function __construct() {
		$args = array(
			'slug'              => 'myplugin-xprofile-fields',
			'name'              => __( 'Profile', 'my-plugin' ),
			'nav_item_name'		  => __( 'Profile', 'my-plugin' ),
			'nav_item_position' => 90,
		);

		parent::init( $args );
	}

	/**
	 * Display the xProfile field group form for the group.
	 *
	 * @param int|null $group_id The ID of the group.
	 */
	public function display( $group_id = null ) : void
	{
		$group_fake_user_id = GROUP_USER_ID_INCREMENT + $group_id;
		$group_type         = bp_groups_get_group_type( $group_id );

		$r = [
			'hide_empty_fields'      => true,
			'fetch_visibility_level' => bp_current_user_can( 'bp_moderate' ) || bp_group_is_admin() || bp_group_is_mod(),
			'user_id'                => $group_fake_user_id,
		];

		if ( $group_type ) {
			// A custom group type is set.
			$r['member_type'] = \MyPlugin\BuddyPress\get_member_type_from_group_type( $group_type );
		}

		if ( ! bp_has_profile( $r ) ) {
		/**
		 * Hey! Regarding `member_type` above - as of BP 14.2.1, it's overriden by fetching the member_type(s) from the specified `user_id`.
		 * As our fake group user IDs intentionally don't exist, this breaks things. :(
		 *
		 * Instead, check out the `filter_bp_get_member_type()` function we've implemented on this project, which implements the same thing on
		 * the `bp_get_member_type()` function which is used by the underlying SQL query which we're unable to modify.
		 *
		 * We're leaving both here in case the internals of `bp_has_profile()` get changed in future versions (and we can remove our workaround).
		 */
		return;
	}

		while ( bp_profile_groups() ) {
			bp_the_profile_group();

			if ( bp_profile_group_has_fields() ) {
			?>

			<div class="<?php bp_the_profile_group_slug(); ?>">
				<?php bp_the_profile_group_name(); ?>

				<table class="profile-fields bp-tables-user">
					<?php
					while ( bp_profile_fields() ) :
						bp_the_profile_field();
					?>

						<?php if ( bp_field_has_data() ) : ?>
							<tr<?php bp_field_css_class(); ?>>
								<td class="label"><?php bp_the_profile_field_name(); ?></td>
								<td class="data"><?php bp_the_profile_field_value(); ?></td>
							</tr>
						<?php endif; ?>

					<?php endwhile; ?>
				</table>
			</div>

			<?php
			}
		}
	}

		/**
	 * Display the edit screen of the xProfile field group form for the group.
	 *
	 * @param int|null $group_id The ID of the group.
	 */
	public function settings_screen( $group_id = null ) : void
	{
		$group_fake_user_id = GROUP_USER_ID_INCREMENT + $group_id;
		$group_type         = bp_groups_get_group_type( $group_id );

		$r = [
			'hide_empty_fields'      => false,
			'fetch_visibility_level' => bp_current_user_can( 'bp_moderate' ) || bp_group_is_admin() || bp_group_is_mod(),
			'user_id'                => $group_fake_user_id,
		];

		if ( $group_type ) {
			// A custom group type is set.
			$r['member_type'] = \MyPlugin\BuddyPress\get_member_type_from_group_type( $group_type );
		}

		if ( ! bp_has_profile( $r ) ) {
			/**
			 * Please read the comment in the `display()` method!
			 */
			return;
		}

		while ( bp_profile_groups() ) :
			bp_the_profile_group();
		?>
			<?php
			while ( bp_profile_fields() ) :
				bp_the_profile_field();
			?>

				<div<?php bp_field_css_class( 'editfield' ); ?>>
					<fieldset>

					<?php
					$field_type = bp_xprofile_create_field_type( bp_get_the_profile_field_type() );
					$field_type->edit_field_html();
					?>

					<?php bp_nouveau_xprofile_edit_visibilty(); ?>

					</fieldset>
				</div>

			<?php endwhile; ?>

			<input type="hidden" name="field_ids" id="field_ids" value="<?php bp_the_profile_field_ids(); ?>" />

		<?php
		endwhile;
	}


	/**
	 * Save the xProfile field group data for the group.
	 *
	 * @param int|null $group_id The ID of the group.
	 */
	public function settings_screen_save( $group_id = null ) : void
	{
		// Check to see if any new information has been submitted.
		if ( empty( $_POST['field_ids'] ) ) {
			return;
		}

		$group_fake_user_id = GROUP_USER_ID_INCREMENT + $group_id;

		// Explode the posted field IDs into an array so we know which fields have been submitted.
		$posted_field_ids = wp_parse_id_list( $_POST['field_ids'] );
		$is_required      = array();

		// Loop through the posted fields formatting any datebox values then validate the field.
		foreach ( (array) $posted_field_ids as $field_id ) {
			bp_xprofile_maybe_format_datebox_post_data( $field_id );

			$is_required[ $field_id ] = xprofile_check_is_required_field( $field_id ) && ! bp_current_user_can( 'bp_moderate' );
			if ( $is_required[ $field_id ] && empty( $_POST[ 'field_' . $field_id ] ) ) {
				$errors = true;
			}
		}

		if ( $errors ) {
			bp_core_add_message( __( 'The changes have not been saved. Please fill in all required fields, and save your changes again.', 'my-plugin' ), 'error' );
			return;
		}

		// Now we've checked for required fields, let's save the values.
		$old_values = $new_values = array();
		foreach ( (array) $posted_field_ids as $field_id ) {

			// Certain types of fields (checkboxes, multiselects) may come through empty. Save them as an empty array so that they don't get overwritten by the default on the next edit.
			$value = isset( $_POST[ 'field_' . $field_id ] ) ? $_POST[ 'field_' . $field_id ] : '';

			$visibility_level = ! empty( $_POST[ 'field_' . $field_id . '_visibility' ] ) ? $_POST[ 'field_' . $field_id . '_visibility' ] : 'public';

			// Save the old and new values. They will be passed to the filter and used to determine whether an activity item should be posted.
			$old_values[ $field_id ] = array(
				'value'      => xprofile_get_field_data( $field_id, $group_fake_user_id ),
				'visibility' => xprofile_get_field_visibility_level( $field_id, $group_fake_user_id ),
			);

			// Update the field data and visibility level.
			xprofile_set_field_visibility_level( $field_id, $group_fake_user_id, $visibility_level );
			$field_updated = xprofile_set_field_data( $field_id, $group_fake_user_id, $value, $is_required[ $field_id ] );
			$value         = xprofile_get_field_data( $field_id, $group_fake_user_id );

			$new_values[ $field_id ] = array(
				'value'      => $value,
				'visibility' => xprofile_get_field_visibility_level( $field_id, $group_fake_user_id ),
			);

			if ( ! $field_updated ) {
				$errors = true;
			}
		}

		// Set the feedback messages.
		if ( $errors ) {
			bp_core_add_message( __( 'There was a problem updating some of the profile information. Please try again.', 'my-plugin' ), 'error' );
		} else {
			bp_core_add_message( __( 'Changes saved.', 'my-plugin' ) );
		}
	}
}