Remove new lines from string and replace with one empty space

$string = "
put returns between paragraphs

for linebreak add 2 spaces at end

";

Want to remove all new lines from string.

I've this regex, it can catch all of them, the problem is I don't know with which function should I use it.

/\r\n|\r|\n/

$string should become:

$string = "put returns between paragraphs for linebreak add 2 spaces at end ";

You have to be cautious of double line breaks, which would cause double spaces. Use this really efficient regular expression:

$string = trim(preg_replace('/\s\s+/', ' ', $string));

Multiple spaces and newlines are replaced with a single space.

Edit: As others have pointed out, this solution has issues matching single newlines in between words. This is not present in the example, but one can easily see how that situation could occur. An alternative is to do the following:

$string = trim(preg_replace('/\s+/', ' ', $string));

A few comments on the accepted answer:

The + means "1 or more". I don't think you need to repeat \s. I think you can simply write '/\s+/'.

Also, if you want to remove whitespace first and last in the string, add trim.

With these modifications, the code would be:

$string = preg_replace('/\s+/', ' ', trim($string));