Regex: Strip non alpha numeric or punctuation

Question

How can I use PHP to strip out all characters that are NOT alpha, numeric, space, or puncutation?

I\'ve tried the following, but it strip punctuation.

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);