(PHP 5 >= 5.1.0)
readline_callback_handler_install — Initializes the readline callback interface and terminal, prints the prompt and returns immediately
   Sets up a readline callback interface then prints
   prompt and immediately returns.  
   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().
promptThe prompt message.
callback
       The callback function takes one parameter; the
       user input returned.
      
   Returns TRUE on success or FALSE on failure.
  
Example #1 Readline Callback Interface Example
<?php
function rl_callback($ret)
{
    global $c, $prompting;
    echo "You entered: $ret\n";
    $c++;
    if ($c > 10) {
        $prompting = false;
        readline_callback_handler_remove();
    } else {
        readline_callback_handler_install("[$c] Enter something: ", 'rl_callback');
    }
}
$c = 1;
$prompting = true;
readline_callback_handler_install("[$c] Enter something: ", 'rl_callback');
while ($prompting) {
    $w = NULL;
    $e = NULL;
    $n = stream_select($r = array(STDIN), $w, $e, null);
    if ($n && in_array(STDIN, $r)) {
        // read a character, will call the callback when a newline is entered
        readline_callback_read_char();
    }
}
echo "Prompting disabled. All done.\n";
?>