The second parameter was added in PHP 4.1.0
This function returns a string with whitespace stripped from the end of str. Without the second parameter, rtrim() will strip these characters:
0x20)), an ordinary space.
0x09)), a tab.
0x0A)), a new line (line feed).
0x0D)), a carriage return.
0x0B)), a vertical tab.
You can also specify the characters you want to strip, by means
of the charlist parameter.
Simply list all characters that you want to be stripped. With
.. you can specify a range of characters.
$text = "\t\tThese are a few words :) ... ";
$trimmed = rtrim($text);
// $trimmed = "\t\tThese are a few words :) ..."
$trimmed = rtrim($text, " \t.");
// $trimmed = "\t\tThese are a few words :)"
$clean = rtrim($binary, "\x00..\x1F");
// trim the ASCII control characters at the end of $binary
// (from 0 to 31 inclusive)