<?php
  
  namespace Guzzle\Http\Message;
  
  /**
   * Request and response message interface
   */
  interface MessageInterface
  {
      /**
       * Get application and plugin specific parameters set on the message.
       *
       * @return \Guzzle\Common\Collection
       */
      public function getParams();
  
      /**
       * Add a header to an existing collection of headers.
       *
       * @param string $header Header name to add
       * @param string $value  Value of the header
       *
       * @return self
       */
      public function addHeader($header, $value);
  
      /**
       * Add and merge in an array of HTTP headers.
       *
       * @param array $headers Associative array of header data.
       *
       * @return self
       */
      public function addHeaders(array $headers);
  
      /**
       * Retrieve an HTTP header by name. Performs a case-insensitive search of all headers.
       *
       * @param string $header Header to retrieve.
       *
       * @return Header|null
       */
      public function getHeader($header);
  
      /**
       * Get all headers as a collection
       *
       * @return \Guzzle\Http\Message\Header\HeaderCollection
       */
      public function getHeaders();
  
      /**
       * Check if the specified header is present.
       *
       * @param string $header The header to check.
       *
       * @return bool
       */
      public function hasHeader($header);
  
      /**
       * Remove a specific HTTP header.
       *
       * @param string $header HTTP header to remove.
       *
       * @return self
       */
      public function removeHeader($header);
  
      /**
       * Set an HTTP header and overwrite any existing value for the header
       *
       * @param string $header Name of the header to set.
       * @param mixed  $value  Value to set.
       *
       * @return self
       */
      public function setHeader($header, $value);
  
      /**
       * Overwrite all HTTP headers with the supplied array of headers
       *
       * @param array $headers Associative array of header data.
       *
       * @return self
       */
      public function setHeaders(array $headers);
  
      /**
       * Get an array of message header lines (e.g. ["Host: example.com", ...])
       *
       * @return array
       */
      public function getHeaderLines();
  
      /**
       * Get the raw message headers as a string
       *
       * @return string
       */
      public function getRawHeaders();
  }