Description
bool 
readline_callback_handler_install ( string prompt, callback callback )
     Sets up a readline callback interface then prints
     prompt and immediately returns. The
     callback function takes one parameter; the user
     input returned. Calling this function twice without removing the previous
     callback interface will automatically and conveniently overwrite the old
     interface.
    
     The callback feature is useful when combined with
     stream_select() as it allows interleaving of IO and
     user input, unlike readline().