Note that this function is blocking if there is no character to read
If you don`t want to get blocked, you should use the trick with stream_select()
It also only reads one char per call,
So if something else in your script is blocking,
you`ve got a problem
(PHP 5 >= 5.1.0)
readline_callback_read_char — Reads a character and informs the readline callback interface when a line is received
Reads a character of user input. When a line is received, this function informs the readline callback interface installed using readline_callback_handler_install() that a line is ready for input.
No devuelve ningún valor.
See readline_callback_handler_install() for an example of how to use the readline callback interface.