Reading an email's subject in Unicode out of an IMAP server

Question

I'm using Zend Framework 1's IMAP server connector and I'm trying to fetch an email from server with Unicode characters in its subject. Here's how I do it:

$message = $imapServer->getMessage($message_number);
echo $message->getHeader('subject');

The problem is that it comes out encoded:

=?UTF-8?B?2KjYp9uM?=

I can find the encoding function within Zend_Mail class named _encodeHeader but I can not find the decoding pair! Does anyone know how to decode this string?

And here's the encoder function:

protected function _encodeHeader($value)
{
    if (Zend_Mime::isPrintable($value) === false) {
        if ($this->getHeaderEncoding() === Zend_Mime::ENCODING_QUOTEDPRINTABLE) {
            $value = Zend_Mime::encodeQuotedPrintableHeader($value, $this->getCharset(), Zend_Mime::LINELENGTH, Zend_Mime::LINEEND);
        } else {
            $value = Zend_Mime::encodeBase64Header($value, $this->getCharset(), Zend_Mime::LINELENGTH, Zend_Mime::LINEEND);
        }
    }

    return $value;
}

Answer 1

Search for a "RFC2047 decoder" and pick one of the existing libraries which does just that. If nothing is usable, roll your own.

Answer 2

Here's how I solved it:

switch (strtolower($encoding)) {
    case \Zend_Mime::ENCODING_QUOTEDPRINTABLE:
        if (preg_match('/^\s?=\?([^\?]+)\?Q\?/', $str, $matches) === 1) {
            $str = preg_replace('/\s?=\?'.preg_quote($matches[1]).'\?Q\?/', ' ', $str);
            $str = strtr($str, array('?=' => ''));
            $str = trim($str);
        }
        return \Zend_Mime_Decode::decodeQuotedPrintable($str);

    case \Zend_Mime::ENCODING_BASE64:
        return base64_decode($encodedText);

    case \Zend_Mime::ENCODING_7BIT:
    case \Zend_Mime::ENCODING_8BIT:
    default:
        return $encodedText;
}