How to remove non alpha numeric characters from a string

This cusom PHP function is designed to remove all characters from a given string that are not alpha numeric. This function is based on preg_replace.

Function

function alphaNumeric($string) {

    return preg_replace("/[^0-9a-zA-Z ]/m", "", $string);
}

Calling The Function

$string = 'ABC-220*_R';

Output

ABC220R