rcube_utils.php

<?php

/*
 +-----------------------------------------------------------------------+
 | program/include/rcube_utils.php                                       |
 |                                                                       |
 | This file is part of the Roundcube Webmail client                     |
 | Copyright (C) 2008-2012, The Roundcube Dev Team                       |
 | Copyright (C) 2011-2012, Kolab Systems AG                             |
 |                                                                       |
 | Licensed under the GNU General Public License version 3 or            |
 | any later version with exceptions for skins & plugins.                |
 | See the README file for a full license statement.                     |
 |                                                                       |
 | PURPOSE:                                                              |
 |   Utility class providing common functions                            |
 +-----------------------------------------------------------------------+
 | Author: Thomas Bruederli <roundcube@gmail.com>                        |
 | Author: Aleksander Machniak <alec@alec.pl>                            |
 +-----------------------------------------------------------------------+
*/


/**
 * Utility class providing common functions
 *
 * @package Core
 */
class rcube_utils
{
    // define constants for input reading
    const INPUT_GET  = 0x0101;
    const INPUT_POST = 0x0102;
    const INPUT_GPC  = 0x0103;

    /**
     * Helper method to set a cookie with the current path and host settings
     *
     * @param string Cookie name
     * @param string Cookie value
     * @param string Expiration time
     */
    public static function setcookie($name, $value, $exp = 0)
    {
        if (headers_sent()) {
            return;
        }

        $cookie = session_get_cookie_params();
        $secure = $cookie['secure'] || self::https_check();

        setcookie($name, $value, $exp, $cookie['path'], $cookie['domain'], $secure, true);
    }

    /**
     * E-mail address validation.
     *
     * @param string $email Email address
     * @param boolean $dns_check True to check dns
     *
     * @return boolean True on success, False if address is invalid
     */
    public static function check_email($email, $dns_check=true)
    {
        // Check for invalid characters
        if (preg_match('/[\x00-\x1F\x7F-\xFF]/', $email)) {
            return false;
        }

        // Check for length limit specified by RFC 5321 (#1486453)
        if (strlen($email) > 254) {
            return false;
        }

        $email_array = explode('@', $email);

        // Check that there's one @ symbol
        if (count($email_array) < 2) {
            return false;
        }

        $domain_part = array_pop($email_array);
        $local_part  = implode('@', $email_array);

        // from PEAR::Validate
        $regexp = '&^(?:
            ("\s*(?:[^"\f\n\r\t\v\b\s]+\s*)+")|                             #1 quoted name
            ([-\w!\#\$%\&\'*+~/^`|{}=]+(?:\.[-\w!\#\$%\&\'*+~/^`|{}=]+)*))  #2 OR dot-atom (RFC5322)
            $&xi';

        if (!preg_match($regexp, $local_part)) {
            return false;
        }

        // Validate domain part
        if (preg_match('/^\[((IPv6:[0-9a-f:.]+)|([0-9.]+))\]$/i', $domain_part, $matches)) {
            return self::check_ip(preg_replace('/^IPv6:/i', '', $matches[1])); // valid IPv4 or IPv6 address
        }
        else {
            // If not an IP address
            $domain_array = explode('.', $domain_part);
            // Not enough parts to be a valid domain
            if (sizeof($domain_array) < 2) {
                return false;
            }

            foreach ($domain_array as $part) {
                if (!preg_match('/^(([A-Za-z0-9][A-Za-z0-9-]{0,61}[A-Za-z0-9])|([A-Za-z0-9]))$/', $part)) {
                    return false;
                }
            }

            // last domain part
            if (preg_match('/[^a-zA-Z]/', array_pop($domain_array))) {
                return false;
            }

            $rcube = rcube::get_instance();

            if (!$dns_check || !$rcube->config->get('email_dns_check')) {
                return true;
            }

            if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN' && version_compare(PHP_VERSION, '5.3.0', '<')) {
                $lookup = array();
                @exec("nslookup -type=MX " . escapeshellarg($domain_part) . " 2>&1", $lookup);
                foreach ($lookup as $line) {
                    if (strpos($line, 'MX preference')) {
                        return true;
                    }
                }
                return false;
            }

            // find MX record(s)
            if (getmxrr($domain_part, $mx_records)) {
                return true;
            }

            // find any DNS record
            if (checkdnsrr($domain_part, 'ANY')) {
                return true;
            }
        }

        return false;
    }


    /**
     * Validates IPv4 or IPv6 address
     *
     * @param string $ip IP address in v4 or v6 format
     *
     * @return bool True if the address is valid
     */
    public static function check_ip($ip)
    {
        // IPv6, but there's no build-in IPv6 support
        if (strpos($ip, ':') !== false && !defined('AF_INET6')) {
            $parts = explode(':', $domain_part);
            $count = count($parts);

            if ($count > 8 || $count < 2) {
                return false;
            }

            foreach ($parts as $idx => $part) {
                $length = strlen($part);
                if (!$length) {
                    // there can be only one ::
                    if ($found_empty) {
                        return false;
                    }
                    $found_empty = true;
                }
                // last part can be an IPv4 address
                else if ($idx == $count - 1) {
                    if (!preg_match('/^[0-9a-f]{1,4}$/i', $part)) {
                        return @inet_pton($part) !== false;
                    }
                }
                else if (!preg_match('/^[0-9a-f]{1,4}$/i', $part)) {
                    return false;
                }
            }

            return true;
        }

        return @inet_pton($ip) !== false;
    }


    /**
     * Check whether the HTTP referer matches the current request
     *
     * @return boolean True if referer is the same host+path, false if not
     */
    public static function check_referer()
    {
        $uri = parse_url($_SERVER['REQUEST_URI']);
        $referer = parse_url(self::request_header('Referer'));
        return $referer['host'] == self::request_header('Host') && $referer['path'] == $uri['path'];
    }


    /**
     * Replacing specials characters to a specific encoding type
     *
     * @param  string  Input string
     * @param  string  Encoding type: text|html|xml|js|url
     * @param  string  Replace mode for tags: show|replace|remove
     * @param  boolean Convert newlines
     *
     * @return string  The quoted string
     */
    public static function rep_specialchars_output($str, $enctype = '', $mode = '', $newlines = true)
    {
        static $html_encode_arr = false;
        static $js_rep_table = false;
        static $xml_rep_table = false;

        if (!is_string($str)) {
            $str = strval($str);
        }

        // encode for HTML output
        if ($enctype == 'html') {
            if (!$html_encode_arr) {
                $html_encode_arr = get_html_translation_table(HTML_SPECIALCHARS);
                unset($html_encode_arr['?']);
            }

            $encode_arr = $html_encode_arr;

            // don't replace quotes and html tags
            if ($mode == 'show' || $mode == '') {
                $ltpos = strpos($str, '<');
                if ($ltpos !== false && strpos($str, '>', $ltpos) !== false) {
                    unset($encode_arr['"']);
                    unset($encode_arr['<']);
                    unset($encode_arr['>']);
                    unset($encode_arr['&']);
                }
            }
            else if ($mode == 'remove') {
                $str = strip_tags($str);
            }

            $out = strtr($str, $encode_arr);

            return $newlines ? nl2br($out) : $out;
        }

        // if the replace tables for XML and JS are not yet defined
        if ($js_rep_table === false) {
            $js_rep_table = $xml_rep_table = array();
            $xml_rep_table['&'] = '&amp;';

            // can be increased to support more charsets
            for ($c=160; $c<256; $c++) {
                $xml_rep_table[chr($c)] = "&#$c;";
            }

            $xml_rep_table['"'] = '&quot;';
            $js_rep_table['"']  = '\\"';
            $js_rep_table["'"]  = "\\'";
            $js_rep_table["\\"] = "\\\\";
            // Unicode line and paragraph separators (#1486310)
            $js_rep_table[chr(hexdec(E2)).chr(hexdec(80)).chr(hexdec(A8))] = '&#8232;';
            $js_rep_table[chr(hexdec(E2)).chr(hexdec(80)).chr(hexdec(A9))] = '&#8233;';
        }

        // encode for javascript use
        if ($enctype == 'js') {
            return preg_replace(array("/\r?\n/", "/\r/", '/<\\//'), array('\n', '\n', '<\\/'), strtr($str, $js_rep_table));
        }

        // encode for plaintext
        if ($enctype == 'text') {
            return str_replace("\r\n", "\n", $mode=='remove' ? strip_tags($str) : $str);
        }

        if ($enctype == 'url') {
            return rawurlencode($str);
        }

        // encode for XML
        if ($enctype == 'xml') {
            return strtr($str, $xml_rep_table);
        }

        // no encoding given -> return original string
        return $str;
    }


    /**
     * Read input value and convert it for internal use
     * Performs stripslashes() and charset conversion if necessary
     *
     * @param  string   Field name to read
     * @param  int      Source to get value from (GPC)
     * @param  boolean  Allow HTML tags in field value
     * @param  string   Charset to convert into
     *
     * @return string   Field value or NULL if not available
     */
    public static function get_input_value($fname, $source, $allow_html=FALSE, $charset=NULL)
    {
        $value = NULL;

        if ($source == self::INPUT_GET) {
            if (isset($_GET[$fname])) {
                $value = $_GET[$fname];
            }
        }
        else if ($source == self::INPUT_POST) {
            if (isset($_POST[$fname])) {
                $value = $_POST[$fname];
            }
        }
        else if ($source == self::INPUT_GPC) {
            if (isset($_POST[$fname])) {
                $value = $_POST[$fname];
            }
            else if (isset($_GET[$fname])) {
                $value = $_GET[$fname];
            }
            else if (isset($_COOKIE[$fname])) {
                $value = $_COOKIE[$fname];
            }
        }

        return self::parse_input_value($value, $allow_html, $charset);
    }


    /**
     * Parse/validate input value. See self::get_input_value()
     * Performs stripslashes() and charset conversion if necessary
     *
     * @param  string   Input value
     * @param  boolean  Allow HTML tags in field value
     * @param  string   Charset to convert into
     *
     * @return string   Parsed value
     */
    public static function parse_input_value($value, $allow_html=FALSE, $charset=NULL)
    {
        global $OUTPUT;

        if (empty($value)) {
            return $value;
        }

        if (is_array($value)) {
            foreach ($value as $idx => $val) {
                $value[$idx] = self::parse_input_value($val, $allow_html, $charset);
            }
            return $value;
        }

        // strip single quotes if magic_quotes_sybase is enabled
        if (ini_get('magic_quotes_sybase')) {
            $value = str_replace("''", "'", $value);
        }
        // strip slashes if magic_quotes enabled
        else if (get_magic_quotes_gpc() || get_magic_quotes_runtime()) {
            $value = stripslashes($value);
        }

        // remove HTML tags if not allowed
        if (!$allow_html) {
            $value = strip_tags($value);
        }

        $output_charset = is_object($OUTPUT) ? $OUTPUT->get_charset() : null;

        // remove invalid characters (#1488124)
        if ($output_charset == 'UTF-8') {
            $value = rcube_charset::clean($value);
        }

        // convert to internal charset
        if ($charset && $output_charset) {
            $value = rcube_charset::convert($value, $output_charset, $charset);
        }

        return $value;
    }


    /**
     * Convert array of request parameters (prefixed with _)
     * to a regular array with non-prefixed keys.
     *
     * @param int    $mode   Source to get value from (GPC)
     * @param string $ignore PCRE expression to skip parameters by name
     *
     * @return array Hash array with all request parameters
     */
    public static function request2param($mode = null, $ignore = 'task|action')
    {
        $out = array();
        $src = $mode == self::INPUT_GET ? $_GET : ($mode == self::INPUT_POST ? $_POST : $_REQUEST);

        foreach ($src as $key => $value) {
            $fname = $key[0] == '_' ? substr($key, 1) : $key;
            if ($ignore && !preg_match('/^(' . $ignore . ')$/', $fname)) {
                $out[$fname] = self::get_input_value($key, $mode);
            }
        }

        return $out;
    }


    /**
     * Convert the given string into a valid HTML identifier
     * Same functionality as done in app.js with rcube_webmail.html_identifier()
     */
    public static function html_identifier($str, $encode=false)
    {
        if ($encode) {
            return rtrim(strtr(base64_encode($str), '+/', '-_'), '=');
        }
        else {
            return asciiwords($str, true, '_');
        }
    }


    /**
     * Create an edit field for inclusion on a form
     *
     * @param string col field name
     * @param string value field value
     * @param array attrib HTML element attributes for field
     * @param string type HTML element type (default 'text')
     *
     * @return string HTML field definition
     */
    public static function get_edit_field($col, $value, $attrib, $type = 'text')
    {
        static $colcounts = array();

        $fname = '_'.$col;
        $attrib['name']  = $fname . ($attrib['array'] ? '[]' : '');
        $attrib['class'] = trim($attrib['class'] . ' ff_' . $col);

        if ($type == 'checkbox') {
            $attrib['value'] = '1';
            $input = new html_checkbox($attrib);
        }
        else if ($type == 'textarea') {
            $attrib['cols'] = $attrib['size'];
            $input = new html_textarea($attrib);
        }
        else if ($type == 'select') {
            $input = new html_select($attrib);
            $input->add('---', '');
            $input->add(array_values($attrib['options']), array_keys($attrib['options']));
        }
        else if ($attrib['type'] == 'password') {
            $input = new html_passwordfield($attrib);
        }
        else {
            if ($attrib['type'] != 'text' && $attrib['type'] != 'hidden') {
                $attrib['type'] = 'text';
            }
            $input = new html_inputfield($attrib);
        }

        // use value from post
        if (isset($_POST[$fname])) {
            $postvalue = self::get_input_value($fname, self::INPUT_POST, true);
            $value = $attrib['array'] ? $postvalue[intval($colcounts[$col]++)] : $postvalue;
        }

        $out = $input->show($value);

        return $out;
    }


    /**
     * Replace all css definitions with #container [def]
     * and remove css-inlined scripting
     *
     * @param string CSS source code
     * @param string Container ID to use as prefix
     *
     * @return string Modified CSS source
     */
    public static function mod_css_styles($source, $container_id, $allow_remote=false)
    {
        $last_pos = 0;
        $replacements = new rcube_string_replacer;

        // ignore the whole block if evil styles are detected
        $source   = self::xss_entity_decode($source);
        $stripped = preg_replace('/[^a-z\(:;]/i', '', $source);
        $evilexpr = 'expression|behavior|javascript:|import[^a]' . (!$allow_remote ? '|url\(' : '');
        if (preg_match("/$evilexpr/i", $stripped)) {
            return '/* evil! */';
        }

        // cut out all contents between { and }
        while (($pos = strpos($source, '{', $last_pos)) && ($pos2 = strpos($source, '}', $pos))) {
            $styles = substr($source, $pos+1, $pos2-($pos+1));

            // check every line of a style block...
            if ($allow_remote) {
                $a_styles = preg_split('/;[\r\n]*/', $styles, -1, PREG_SPLIT_NO_EMPTY);
                foreach ($a_styles as $line) {
                    $stripped = preg_replace('/[^a-z\(:;]/i', '', $line);
                    // ... and only allow strict url() values
                    $regexp = '!url\s*\([ "\'](https?:)//[a-z0-9/._+-]+["\' ]\)!Uims';
                    if (stripos($stripped, 'url(') && !preg_match($regexp, $line)) {
                        $a_styles = array('/* evil! */');
                        break;
                    }
                }
                $styles = join(";\n", $a_styles);
            }

            $key = $replacements->add($styles);
            $source = substr($source, 0, $pos+1)
                . $replacements->get_replacement($key)
                . substr($source, $pos2, strlen($source)-$pos2);
            $last_pos = $pos+2;
        }

        // remove html comments and add #container to each tag selector.
        // also replace body definition because we also stripped off the <body> tag
        $styles = preg_replace(
            array(
                '/(^\s*<!--)|(-->\s*$)/',
                '/(^\s*|,\s*|\}\s*)([a-z0-9\._#\*][a-z0-9\.\-_]*)/im',
                '/'.preg_quote($container_id, '/').'\s+body/i',
            ),
            array(
                '',
                "\\1#$container_id \\2",
                $container_id,
            ),
            $source);

        // put block contents back in
        $styles = $replacements->resolve($styles);

        return $styles;
    }


    /**
     * Generate CSS classes from mimetype and filename extension
     *
     * @param string $mimetype  Mimetype
     * @param string $filename  Filename
     *
     * @return string CSS classes separated by space
     */
    public static function file2class($mimetype, $filename)
    {
        list($primary, $secondary) = explode('/', $mimetype);

        $classes = array($primary ? $primary : 'unknown');
        if ($secondary) {
            $classes[] = $secondary;
        }
        if (preg_match('/\.([a-z0-9]+)$/i', $filename, $m)) {
            $classes[] = $m[1];
        }

        return strtolower(join(" ", $classes));
    }


    /**
     * Decode escaped entities used by known XSS exploits.
     * See http://downloads.securityfocus.com/vulnerabilities/exploits/26800.eml for examples
     *
     * @param string CSS content to decode
     *
     * @return string Decoded string
     */
    public static function xss_entity_decode($content)
    {
        $out = html_entity_decode(html_entity_decode($content));
        $out = preg_replace_callback('/\\\([0-9a-f]{4})/i',
            array(self, 'xss_entity_decode_callback'), $out);
        $out = preg_replace('#/\*.*\*/#Ums', '', $out);

        return $out;
    }


    /**
     * preg_replace_callback callback for xss_entity_decode
     *
     * @param array $matches Result from preg_replace_callback
     *
     * @return string Decoded entity
     */
    public static function xss_entity_decode_callback($matches)
    {
        return chr(hexdec($matches[1]));
    }


    /**
     * Check if we can process not exceeding memory_limit
     *
     * @param integer Required amount of memory
     *
     * @return boolean True if memory won't be exceeded, False otherwise
     */
    public static function mem_check($need)
    {
        $mem_limit = parse_bytes(ini_get('memory_limit'));
        $memory    = function_exists('memory_get_usage') ? memory_get_usage() : 16*1024*1024; // safe value: 16MB

        return $mem_limit > 0 && $memory + $need > $mem_limit ? false : true;
    }


    /**
     * Check if working in SSL mode
     *
     * @param integer $port      HTTPS port number
     * @param boolean $use_https Enables 'use_https' option checking
     *
     * @return boolean
     */
    public static function https_check($port=null, $use_https=true)
    {
        global $RCMAIL;

        if (!empty($_SERVER['HTTPS']) && strtolower($_SERVER['HTTPS']) != 'off') {
            return true;
        }
        if (!empty($_SERVER['HTTP_X_FORWARDED_PROTO']) && strtolower($_SERVER['HTTP_X_FORWARDED_PROTO']) == 'https') {
            return true;
        }
        if ($port && $_SERVER['SERVER_PORT'] == $port) {
            return true;
        }
        if ($use_https && isset($RCMAIL) && $RCMAIL->config->get('use_https')) {
            return true;
        }

        return false;
    }


    /**
     * Replaces hostname variables.
     *
     * @param string $name Hostname
     * @param string $host Optional IMAP hostname
     *
     * @return string Hostname
     */
    public static function parse_host($name, $host = '')
    {
        // %n - host
        $n = preg_replace('/:\d+$/', '', $_SERVER['SERVER_NAME']);
        // %t - host name without first part, e.g. %n=mail.domain.tld, %t=domain.tld
        $t = preg_replace('/^[^\.]+\./', '', $n);
        // %d - domain name without first part
        $d = preg_replace('/^[^\.]+\./', '', $_SERVER['HTTP_HOST']);
        // %h - IMAP host
        $h = $_SESSION['storage_host'] ? $_SESSION['storage_host'] : $host;
        // %z - IMAP domain without first part, e.g. %h=imap.domain.tld, %z=domain.tld
        $z = preg_replace('/^[^\.]+\./', '', $h);
        // %s - domain name after the '@' from e-mail address provided at login screen. Returns FALSE if an invalid email is provided
        if (strpos($name, '%s') !== false) {
            $user_email = self::get_input_value('_user', self::INPUT_POST);
            $user_email = self::idn_convert($user_email, true);
            $matches    = preg_match('/(.*)@([a-z0-9\.\-\[\]\:]+)/i', $user_email, $s);
            if ($matches < 1 || filter_var($s[1]."@".$s[2], FILTER_VALIDATE_EMAIL) === false) {
                return false;
            }
        }

        $name = str_replace(array('%n', '%t', '%d', '%h', '%z', '%s'), array($n, $t, $d, $h, $z, $s[2]), $name);
        return $name;
    }


    /**
     * Returns remote IP address and forwarded addresses if found
     *
     * @return string Remote IP address(es)
     */
    public static function remote_ip()
    {
        $address = $_SERVER['REMOTE_ADDR'];

        // append the NGINX X-Real-IP header, if set
        if (!empty($_SERVER['HTTP_X_REAL_IP'])) {
            $remote_ip[] = 'X-Real-IP: ' . $_SERVER['HTTP_X_REAL_IP'];
        }
        // append the X-Forwarded-For header, if set
        if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
            $remote_ip[] = 'X-Forwarded-For: ' . $_SERVER['HTTP_X_FORWARDED_FOR'];
        }

        if (!empty($remote_ip)) {
            $address .= '(' . implode(',', $remote_ip) . ')';
        }

        return $address;
    }


    /**
     * Read a specific HTTP request header.
     *
     * @param  string $name Header name
     *
     * @return mixed  Header value or null if not available
     */
    public static function request_header($name)
    {
        if (function_exists('getallheaders')) {
            $hdrs = array_change_key_case(getallheaders(), CASE_UPPER);
            $key  = strtoupper($name);
        }
        else {
            $key  = 'HTTP_' . strtoupper(strtr($name, '-', '_'));
            $hdrs = array_change_key_case($_SERVER, CASE_UPPER);
        }

        return $hdrs[$key];
    }

    /**
     * Explode quoted string
     *
     * @param string Delimiter expression string for preg_match()
     * @param string Input string
     *
     * @return array String items
     */
    public static function explode_quoted_string($delimiter, $string)
    {
        $result = array();
        $strlen = strlen($string);

        for ($q=$p=$i=0; $i < $strlen; $i++) {
            if ($string[$i] == "\"" && $string[$i-1] != "\\") {
                $q = $q ? false : true;
            }
            else if (!$q && preg_match("/$delimiter/", $string[$i])) {
                $result[] = substr($string, $p, $i - $p);
                $p = $i + 1;
            }
        }

        $result[] = substr($string, $p);

        return $result;
    }


    /**
     * Improved equivalent to strtotime()
     *
     * @param string $date  Date string
     *
     * @return int Unix timestamp
     */
    public static function strtotime($date)
    {
        // check for MS Outlook vCard date format YYYYMMDD
        if (preg_match('/^([12][90]\d\d)([01]\d)(\d\d)$/', trim($date), $matches)) {
            return mktime(0,0,0, intval($matches[2]), intval($matches[3]), intval($matches[1]));
        }
        else if (is_numeric($date)) {
            return $date;
        }

        // support non-standard "GMTXXXX" literal
        $date = preg_replace('/GMT\s*([+-][0-9]+)/', '\\1', $date);

        // if date parsing fails, we have a date in non-rfc format.
        // remove token from the end and try again
        while ((($ts = @strtotime($date)) === false) || ($ts < 0)) {
            $d = explode(' ', $date);
            array_pop($d);
            if (!$d) {
                break;
            }
            $date = implode(' ', $d);
        }

        return $ts;
    }


    /*
     * Idn_to_ascii wrapper.
     * Intl/Idn modules version of this function doesn't work with e-mail address
     */
    public static function idn_to_ascii($str)
    {
        return self::idn_convert($str, true);
    }


    /*
     * Idn_to_ascii wrapper.
     * Intl/Idn modules version of this function doesn't work with e-mail address
     */
    public static function idn_to_utf8($str)
    {
        return self::idn_convert($str, false);
    }


    public static function idn_convert($input, $is_utf=false)
    {
        if ($at = strpos($input, '@')) {
            $user   = substr($input, 0, $at);
            $domain = substr($input, $at+1);
        }
        else {
            $domain = $input;
        }

        $domain = $is_utf ? idn_to_ascii($domain) : idn_to_utf8($domain);

        if ($domain === false) {
            return '';
        }

        return $at ? $user . '@' . $domain : $domain;
    }

    /**
     * Split the given string into word tokens
     *
     * @param string Input to tokenize
     * @return array List of tokens
     */
    public static function tokenize_string($str)
    {
        return explode(" ", preg_replace(
            array('/[\s;\/+-]+/i', '/(\d)[-.\s]+(\d)/', '/\s\w{1,3}\s/u'),
            array(' ', '\\1\\2', ' '),
            $str));
    }

    /**
     * Normalize the given string for fulltext search.
     * Currently only optimized for Latin-1 characters; to be extended
     *
     * @param string  Input string (UTF-8)
     * @param boolean True to return list of words as array
     * @return mixed  Normalized string or a list of normalized tokens
     */
    public static function normalize_string($str, $as_array = false)
    {
        // split by words
        $arr = self::tokenize_string($str);

        foreach ($arr as $i => $part) {
            if (utf8_encode(utf8_decode($part)) == $part) {  // is latin-1 ?
                $arr[$i] = utf8_encode(strtr(strtolower(strtr(utf8_decode($part),
                    'ÇçäâàåéêëèïîìÅÉöôòüûùÿøØáíóúñÑÁÂÀãÃÊËÈÍÎÏÓÔõÕÚÛÙýÝ',
                    'ccaaaaeeeeiiiaeooouuuyooaiounnaaaaaeeeiiioooouuuyy')),
                    array('ß' => 'ss', 'ae' => 'a', 'oe' => 'o', 'ue' => 'u')));
            }
            else
                $arr[$i] = mb_strtolower($part);
        }

        return $as_array ? $arr : join(" ", $arr);
    }

}