What are the differences between carriage return (cr), linefeed (lf), and crlf in terms of representing line breaks in PHP and how should they be handled?

When dealing with line breaks in PHP, it's important to understand the differences between carriage return (CR), linefeed (LF), and carriage return followed by linefeed (CRLF). In PHP, the newline character is represented by "\n" which is equivalent to LF. However, different operating systems use different conventions for line breaks - Windows uses CRLF, Unix/Linux uses LF, and older Mac systems use CR. To handle line breaks consistently in PHP, you can use the PHP_EOL constant which represents the correct newline character for the current platform. This ensures that your code will work correctly across different operating systems.

// Using PHP_EOL to handle line breaks
$text = "This is a line of text." . PHP_EOL;
file_put_contents('file.txt', $text, FILE_APPEND);