How can i turn multiple line breaks into one with preg_replace?

Hello,

I get to many line breaks from an input. How can i turn multiple line breaks into one?

This code works to turn multiple spaces into one.

$description = preg_replace('~[\r\n\s\t]+~', ' ', $description);

PHP:

I want to do the same for line breaks aswell. but i do not know how to do

Thanks