PHP newline not working in text file

Question

I am using the PHP code:

$numberNewline = $number . \'\\n\';
fwrite($file, $numberNewline);

to write $number to a file.

For some reason

Answer 1

'\n' in single quotes is a literal \n.
"\n" in double quotes is interpreted as a line break.

http://php.net/manual/en/language.types.string.php