The http://api.libssh.org/master/libssh_tutor_shell.html#select_loop part of tutorial is called "A more elaborate way to get the remote data" and starts with note
Warning: ssh_select() and ssh_channel_select() are not relevant anymore, since libssh is about to provide an easier system for asynchronous communications. This subsection should be removed then. ***
This warning is there at least since 2010, added via 94b689e19d51ab887afe95afd8e9bf50a18af0c4. Either the no-longer-relevant ssh_select() and ssh_channel_select() examples should be replaced by the better way of doing things, or we should accept that there isn't a better way coming and this warning should be removed.
Otherwise people who try to follow the tutorial have no idea if they should write new code using ssh_select()/ssh_channel_select() or how long to wait for the better mechanism.