Stripping everything but alphanumeric chars from a string in PHP

Question

I\'d like a regexp or other string which can replace everything except alphanumeric chars (a-z and 0-9) from a string. All things such as ,@#

Answer 1

$string = preg_replace("/[^a-z0-9.]+/i", "", $string);

Matches one or more characters not a-z 0-9 [case-insensitive], or "." and replaces with ""