Carriage Return
A carriage return is a whitespace character, that historically represents moving the cursor to the beginning of the line, without changing line. It is often combined to the line feed: on a typewriter, that combination is needed to move the carriage to the beginning of the next line. This does not apply anymore on computers.
A carriage return is represented by the escape sequence \r, in double quote strings. It is also the ASCII code 13.
Carriage return are important when formatting code, as they are at the end of a line.
<?php
echo "\r";
echo chr(13); // ASCII code 13
?>