Question

I am trying to read emails through Exchange Server 2003 through a URL in PHP. Files that have characters not allowed in filenames convert them into some form of Unicode. For e.g / is converted to xF8FF and \ is converted to xF8FE

How can I use PHP to convert these characters into the correct encoding? I know I could take a long way around and use str_replace, but I know that other characters such as : ; * < > will have the same problem. Does PHP support this encoding natively?

Thanks

Answer 1

Starting from the source code of the Ximian Connector for Microsoft Exchange (written in the C programming language), I’ve made up this sample of PHP code:

<?php

class myExchange {
    private $uri_encoded_char = array(
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 0x00 - 0x0f */
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  /* 0x10 - 0x1f */
        1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 2,  /*  ' ' - '/'  */
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 2,  /*  '0' - '?'  */
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /*  '@' - 'O'  */
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 1, 1, 0,  /*  'P' - '_'  */
        1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  /*  '`' - 'o'  */
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 1,  /*  'p' - 0x7f */
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
    );

    /**
     * e2k_uri_append_encoded: 
     *  
     * Appends $in to $str, encoding URI-unsafe characters as needed
     * (optionally including some Exchange-specific encodings).
     * When appending a path, you must append each segment separately;
     * e2k_uri_append_encoded() will encode any "/"s passed in.
     *  
     * @param string $str               a string containing part of a URI
     * @param string $in                data to append to $str
     * @param bool   $wss_encode        whether or not to use the 
     *                                  special Web Storage System
     *                                  encoding rules
     * @param string $extra_enc_chars   additional characters beyond 
     *                                  the normal URI-reserved
     *                                  characters to encode when
     *                                  appending to $str
     * @return string  
     **/
    public function e2k_uri_append_encoded($str, $in, $wss_encode, $extra_enc_chars) {
        $len = strlen($in);
        for ($i = 0; $i < $len; $i++) {
            $s = $in[$i];
            $c = ord($s);
            if ($extra_enc_chars && strchr($extra_enc_chars, $s)) {
                $str .= sprintf("%%%02x", $c);
            } else {
                switch ($this->uri_encoded_char[$c]) {
                    case 2:
                        if (!$wss_encode) {
                            $str .= sprintf("%%%02x", $c);
                        } else {
                            switch ($s) {
                                case '/':
                                    $str .= "_xF8FF_";
                                    break;
                                case '?':
                                    $str .= "_x003F_";
                                    break;
                                case '\\':
                                    $str .= "_xF8FE_";
                                    break;
                                case '~':
                                    $str .= "_x007E_";
                                    break;
                            }
                        }
                        break;
                    case 1:
                        $str .= sprintf("%%%02x", $c);
                        break;
                    default:
                        $str .= $s;
                        break;
                }
            }
        }
        return($str);
    }
}

$filename = "@#£¤$%&/{([)]=}+?'`|~,;.:-_<>æøåäâãëêïîöôõüûÿ\\.EML";

$e = new myExchange();
echo $e->e2k_uri_append_encoded("", $filename, true, null);
echo "\n";

?>

Here is the output:

@%23%a3%a4$%25%26_xF8FF_%7b(%5b)%5d=%7d+_x003F_'%60%7c_x007E_,;.:-_%3c%3e%e6%f8%e5%e4%e2%e3%eb%ea%ef%ee%f6%f4%f5%fc%fb%ff_xF8FE_.EML

Unfortunately I don’t have an Exchange Server, so I can’t tell if it really works, however I hope it can be a good starting point.