src/Header.php
public function add(array $headers) {
        foreach ($headers as $key => $values) {
            $this->set($key, $values);
        }
        return $this;
    }
public function add(array $headers) {
        foreach ($headers as $key => $values) {
            $this->set($key, $values);
        }
        return $this;
    }
Adds new headers the current HTTP headers set.

@param array $headers An array of HTTP headers
@return $this