function xprofile_ajax_reorder_fields() {
	// Check the nonce.
	check_admin_referer( 'bp_reorder_fields', '_wpnonce_reorder_fields' );

	if ( empty( $_POST['field_order'] ) ) {
		return wp_send_json_error();
	}

	$field_group_id = $_POST['field_group_id'];
	$group_tab      = '';

	if ( isset( $_POST['group_tab'] ) && $_POST['group_tab'] ) {
		$group_tab = wp_unslash( $_POST['group_tab'] );
	}

	if ( 'signup-fields' === $field_group_id ) {
		parse_str( $_POST['field_order'], $order );
		$fields = (array) $order['draggable_signup_field'];
		$fields = array_map( 'intval', $fields );

		if ( isset( $_POST['new_signup_field_id'] ) && $_POST['new_signup_field_id'] ) {
			parse_str( $_POST['new_signup_field_id'], $signup_field );
			$signup_fields = (array) $signup_field['draggable_signup_field'];
		}

		// Adding a new field to the registration form.
		if ( 'signup-group' === $group_tab ) {
			$field_id = (int) reset( $signup_fields );

			// Load the field.
			$field = xprofile_get_field( $field_id, null, false );

			if ( $field instanceof BP_XProfile_Field ) {
				// The field doesn't support the feature, stop right away!
				if ( ! $field->field_type_supports( 'signup_position' ) ) {
					wp_send_json_error(
						array(
							'message' => __( 'This field cannot be inserted into the registration form.', 'buddypress' ),
						)
					);
				}

				$signup_position = bp_xprofile_get_meta( $field->id, 'field', 'signup_position' );

				if ( ! $signup_position ) {
					$position = array_search( $field->id, $fields, true );
					if ( false !== $position ) {
						$position += 1;
					} else {
						$position = 1;
					}

					// Set the signup position.
					bp_xprofile_update_field_meta( $field->id, 'signup_position', $position );

					// Get the real Group object.
					$group = xprofile_get_field_group( $field->id );

					// Gets the HTML Output of the signup field.
					$signup_field = bp_xprofile_admin_get_signup_field( $field, $group );

					/**
					 * Fires once a signup field has been inserted.
					 *
					 * @since 8.0.0
					 */
					do_action( 'bp_xprofile_inserted_signup_field' );

					// Send the signup field to output.
					wp_send_json_success(
						array(
							'signup_field' => $signup_field,
							'field_id'     => $field->id,
						)
					);
				} else {
					wp_send_json_error(
						array(
							'message' => __( 'This field has been already added to the registration form.', 'buddypress' ),
						)
					);
				}

			} else {
				wp_send_json_error();
			}
		} else {
			// it's a sort operation.
			foreach ( $fields as $position => $field_id ) {
				bp_xprofile_update_field_meta( (int) $field_id, 'signup_position', (int) $position + 1 );
			}

			/**
			 * Fires once the signup fields have been reordered.
			 *
			 * @since 8.0.0
			 */
			do_action( 'bp_xprofile_reordered_signup_fields' );

			wp_send_json_success();
		}
	} else {
		/**
		 * @todo there's something going wrong here.
		 * moving a field to another tab when there's only the fullname field fails.
		 */
		parse_str( $_POST['field_order'], $order );
		$fields = (array) $order['draggable_field'];

		foreach ( $fields as $position => $field_id ) {
			xprofile_update_field_position( (int) $field_id, (int) $position, (int) $field_group_id );
		}

		wp_send_json_success();
	}
}