public static function parse($headers) {
       $fields = explode("\r\n", preg_replace('/\x0D\x0A[\x09\x20]+/', ' ', $headers));

       if(empty($fields)) return [];

       return array_reduce($fields, function($carry, $field) {
           $match = [];
           if (!preg_match('/([^:]+): (.+)/m', $field, $match)) return $carry;

           $match[1] = preg_replace_callback('/(?<=^|[\x09\x20\x2D])./',function($matches) {
               return strtoupper($matches[0]);
           }, strtolower(trim($match[1])));

           if (!isset($carry[$match[1]])) {
               $carry[$match[1]] = trim($match[2]);
               return $carry;
           }
           
           if (is_array($carry[$match[1]])) {
               $carry[$match[1]][] = trim($match[2]);      
               return $carry;
           }
           
           $carry[$match[1]] = [$carry[$match[1]], trim($match[2])];

           return $carry;
       }, []);
    }