将两个换行符转换为一个换行符[重复]

Question

This question already has an answer here:

• Replace multiple newlines, tabs, and spaces 10 answers

Let's say for example somebody enters into a textarea:

line
line

I want it to be displayed as

line line

And if someone enters

line

line

It displays as

line
line

Stackoverflow does this too, but I want to know how to do it specifically with PHP.

Thanks.

</div>

Answer 1

You can use this:

$search = ['~(?<!\s)\h*\R\h*+(?!\s)~', '~\h*(\R)\h*+\s+~'];
$replace = [' ', '$1'];

$str = preg_replace($search, $replace, $str);

Where \R is a linebreak (whatever the OS). \h is an horizontal whitespace and is used here to trim leading and trailing spaces. (to be more rigorous, you can replace all \h with [^\S ])