How can I decode a string that has been encoded using RFC2231 using PHP

Question

I am parsing MIME formatted emails which have attachments. The attachments have their filenames encoded using RFC2231, so for example the 'content-disposition' of one of the attached files is:

attachment;  filename*=utf-8''Bill%20Sixteen.pdf

How do I go about decoding that filename?

Answer 1

Here is the specific method out of the akelos framework as mentioned by Dukeatcoding.

/**
 * RFC 2231 Implementation
 */
public function _decodeHeaderAttribute($header_attribute, $charset = '')
{
    if(preg_match("/^([A-Z0-9\-]+)(\'[A-Z\-]{2,5}\')?/i",$header_attribute,$match)){
        $charset = $match[1];
        $header_attribute = urldecode(str_replace(array('_','='),array('%20','%'), substr($header_attribute,strlen($match[0]))));
    }
    return Ak::recode($header_attribute, 'UTF-8', $charset);
}

See how they do it and create your own decode function using that ;)

P.S. I believe that the akelos framework uses the LGLP license - so be warned should you use that method as is in your own project.