How does Stack Overflow generate its SEO-friendly URLs?

Question

What is a good complete regular expression or some other process that would take the title:

How do you change a title to be part of the URL like Stack

Answer 1

No, no, no. You are all so very wrong. Except for the diacritics-fu stuff, you're getting there, but what about Asian characters (shame on Ruby developers for not considering their nihonjin brethren).

Firefox and Safari both display non-ASCII characters in the URL, and frankly they look great. It is nice to support links like 'http://somewhere.com/news/read/お前たちはアホじゃないかい'.

So here's some PHP code that'll do it, but I just wrote it and haven't stress tested it.

 1 && mb_strlen($c)===1)
            {
                $real_slug .= $hyphen . $c;
                $hyphen = '';
            }
            else
            {
                switch($c)
                {
                    case '&':
                        $hyphen = $real_slug ? '-and-' : '';
                        break;
                    case 'a':
                    case 'b':
                    case 'c':
                    case 'd':
                    case 'e':
                    case 'f':
                    case 'g':
                    case 'h':
                    case 'i':
                    case 'j':
                    case 'k':
                    case 'l':
                    case 'm':
                    case 'n':
                    case 'o':
                    case 'p':
                    case 'q':
                    case 'r':
                    case 's':
                    case 't':
                    case 'u':
                    case 'v':
                    case 'w':
                    case 'x':
                    case 'y':
                    case 'z':

                    case 'A':
                    case 'B':
                    case 'C':
                    case 'D':
                    case 'E':
                    case 'F':
                    case 'G':
                    case 'H':
                    case 'I':
                    case 'J':
                    case 'K':
                    case 'L':
                    case 'M':
                    case 'N':
                    case 'O':
                    case 'P':
                    case 'Q':
                    case 'R':
                    case 'S':
                    case 'T':
                    case 'U':
                    case 'V':
                    case 'W':
                    case 'X':
                    case 'Y':
                    case 'Z':

                    case '0':
                    case '1':
                    case '2':
                    case '3':
                    case '4':
                    case '5':
                    case '6':
                    case '7':
                    case '8':
                    case '9':
                        $real_slug .= $hyphen . $c;
                        $hyphen = '';
                        break;

                    default:
                       $hyphen = $hyphen ? $hyphen : ($real_slug ? '-' : '');
                }
            }
        }
        return $real_slug;
    }

Example:

$str = "~!@#$%^&*()_+-=[]\{}|;':\",./<>?\n\r\t\x07\x00\x04 コリン ~!@#$%^&*()_+-=[]\{}|;':\",./<>?\n\r\t\x07\x00\x04 トーマス ~!@#$%^&*()_+-=[]\{}|;':\",./<>?\n\r\t\x07\x00\x04 アーノルド ~!@#$%^&*()_+-=[]\{}|;':\",./<>?\n\r\t\x07\x00\x04";
echo slug($str);

Outputs: コリン-and-トーマス-and-アーノルド

The '-and-' is because &'s get changed to '-and-'.