bp_member_switch_to( int $user_id, bool $remember = false, bool $set_old_user = true )

function bp_member_switch_to( $user_id, $remember = false, $set_old_user = true ) {
	$user = get_userdata( $user_id );

	if ( ! $user ) {
		return false;
	}

	$old_user_id  = ( is_user_logged_in() ) ? get_current_user_id() : false;
	$old_token    = function_exists( 'wp_get_session_token' ) ? wp_get_session_token() : '';
	$auth_cookie  = bp_member_switching_get_auth_cookie();
	$cookie_parts = wp_parse_auth_cookie( end( $auth_cookie ) );

	if ( $set_old_user && $old_user_id ) {
		// Switching to another user
		$new_token = '';
		// We'll not override the old user
		if ( empty( $auth_cookie ) ) {
			bp_member_switching_set_olduser_cookie( $old_user_id, false, $old_token );
		}
	} else {
		// Switching back, either after being switched off or after being switched to another user
		$new_token = isset( $cookie_parts['token'] ) ? $cookie_parts['token'] : '';
		bp_member_switching_clear_olduser_cookie( false );
	}

	/**
	 * Attaches the original user ID and session token to the new session when a user switches to another user.
	 *
	 * @param array $session Array of extra data.
	 * @param int $user_id User ID.
	 *
	 * @return array Array of extra data.
	 */
	$session_filter = function ( array $session, $user_id ) use ( $old_user_id, $old_token ) {
		$session['switched_from_id']      = $old_user_id;
		$session['switched_from_session'] = $old_token;

		return $session;
	};

	add_filter( 'attach_session_information', $session_filter, 99, 2 );

	wp_clear_auth_cookie();
	wp_set_auth_cookie( $user_id, $remember, '', $new_token );
	wp_set_current_user( $user_id );

	if ( $old_token && $old_user_id && ! $set_old_user ) {
		// When switching back, destroy the session for the old user
		$manager = WP_Session_Tokens::get_instance( $old_user_id );
		$manager->destroy( $old_token );
	}

	return $user;
}