replace characters that are hidden in text

Question

How to remove   (that are hidden) and SPACES in below text but

• hold UNICODE characters
• hold
tag

Answer 1

All solutions above kind of work, until one starts to work with German language where there are such letters:

ä ä

and othere simial ones. I use the following code:

$string = preg_replace ( "!\s++!u", ' ', $string );

More details here: PCRE(3) Library Functions Manual