public function createPost($gid, $title, $summary = '') {
		if(!is_string($gid)) {
			throw new LinkedInException('LinkedIn->createPost(): bad data passed, $gid must be of type string.');
		}
		if(!is_string($title) || empty($title)) {
			throw new LinkedInException('LinkedIn->createPost(): bad data passed, $title must be a non-empty string.');
		}
		if(!is_string($summary)) {
			throw new LinkedInException('LinkedIn->createPost(): bad data passed, $summary must be of type string.');
		}
		
		// construct the XML
		$data = '<?xml version="1.0" encoding="UTF-8"?>
    				 <post>
    					 <title>'. $title . '</title>
    					 <summary>' . $summary . '</summary>
    				 </post>';
		
 		// construct and send the request
		$query    = self::_URL_API . '/v1/groups/' . trim($gid) . '/posts';
		$response = $this->fetch('POST', $query, $data);
		
	  /**
	   * Check for successful request (a 201 response from LinkedIn server) 
	   * per the documentation linked in method comments above.
	   */
		return $this->checkResponse(201, $response);
	}