Strip all non-alphanumeric, spaces and punctuation symbols from a string

Question

How can I use PHP to strip out all characters that are NOT letters, numbers, spaces, or punctuation marks?

I've tried the following, but it strips punctuation.

preg_replace("/[^a-zA-Z0-9\s]/", "", $str);

Answer 1

preg_replace("/[^a-zA-Z0-9\s\p{P}]/", "", $str);

Example:

php > echo preg_replace("/[^a-zA-Z0-9\s\p{P}]/", "", "⟺f✆oo☃. ba⟗r!");
foo. bar!

\p{P} matches all Unicode punctuation characters (see Unicode character properties). If you only want to allow specific punctuation, simply add them to the negated character class. E.g:

preg_replace("/[^a-zA-Z0-9\s.?!]/", "", $str);