public static function parseHeaders($headerstr=false) {
        if ( $headerstr === false ) $headerstr = self::getLastHeadersReceived();
        $lines = explode("\n",$headerstr);
        $headermap = array();

        foreach ($lines as $line) {
            $pos = strpos($line, ':');
            if ( $pos < 1 ) continue;
            $key = substr($line,0,$pos);
            $value = trim(substr($line, $pos+1));
            if ( strlen($key) < 1 || strlen($value) < 1 ) continue;
            $headermap[$key] = $value;
        }
        return $headermap;
    }