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

$str = trim($str);
$str = trim($str, "\x00..\x1F");
$str = str_replace(array( ""","'","&","<",">"),' ',$str);
$str = preg_replace('/[^0-9a-zA-Z-]/', ' ', $str);
$str = preg_replace('/\s\s+/', ' ', $str); 
$str = trim($str);
$str = preg_replace('/[ ]/', '-', $str);

Hope this helps.