Converts a string into a slug. http://en.wikipedia.org/wiki/Slug_(web_publishing)#Slug

slugify.php

<?php
function slugify($string) {
    $string = preg_replace('/
        [\x09\x0A\x0D\x20-\x7E]              # ASCII
        | [\xC2-\xDF][\x80-\xBF]             # non-overlong 2-byte
        |  \xE0[\xA0-\xBF][\x80-\xBF]        # excluding overlongs
        | [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}  # straight 3-byte
        |  \xED[\x80-\x9F][\x80-\xBF]        # excluding surrogates
        |  \xF0[\x90-\xBF][\x80-\xBF]{2}     # planes 1-3
        | [\xF1-\xF3][\x80-\xBF]{3}          # planes 4-15
        |  \xF4[\x80-\x8F][\x80-\xBF]{2}     # plane 16
        /', '', $string);
    // @see https://github.com/cocur/slugify/blob/master/src/Cocur/Slugify/Slugify.php

    // transliterate
    $string = iconv('utf-8', 'us-ascii//TRANSLIT', $string);
    // replace non letter or digits by seperator
    $string = preg_replace('#[^\\pL\d]+#u', $separator, $string);
    // trim
    $string = trim($string, $separator);
    // lowercase
    $string = (defined('MB_CASE_LOWER')) ? mb_strtolower($string) : strtolower($string);
    // remove unwanted characters
    $string = preg_replace('#[^-\w]+#', '', $string);

    return $string;
}