The Recess! Framework uses the following class which provides constants and simple helper methods for HTTP Response Status Codes.

<?php
/**
 * StatusCodes provides named constants for
 * HTTP protocol status codes. Written for the
 * Recess Framework (http://www.recessframework.com/)
 *
 * @author Kris Jordan
 * @license MIT
 * @package recess.http
 */
class StatusCodes {
	// [Informational 1xx]
	const HTTP_CONTINUE = 100;
	const HTTP_SWITCHING_PROTOCOLS = 101;
	// [Successful 2xx]
	const HTTP_OK = 200;
	const HTTP_CREATED = 201;
	const HTTP_ACCEPTED = 202;
	const HTTP_NONAUTHORITATIVE_INFORMATION = 203;
	const HTTP_NO_CONTENT = 204;
	const HTTP_RESET_CONTENT = 205;
	const HTTP_PARTIAL_CONTENT = 206;
	// [Redirection 3xx]
	const HTTP_MULTIPLE_CHOICES = 300;
	const HTTP_MOVED_PERMANENTLY = 301;
	const HTTP_FOUND = 302;
	const HTTP_SEE_OTHER = 303;
	const HTTP_NOT_MODIFIED = 304;
	const HTTP_USE_PROXY = 305;
	const HTTP_UNUSED= 306;
	const HTTP_TEMPORARY_REDIRECT = 307;
	// [Client Error 4xx]
	const errorCodesBeginAt = 400;
	const HTTP_BAD_REQUEST = 400;
	const HTTP_UNAUTHORIZED  = 401;
	const HTTP_PAYMENT_REQUIRED = 402;
	const HTTP_FORBIDDEN = 403;
	const HTTP_NOT_FOUND = 404;
	const HTTP_METHOD_NOT_ALLOWED = 405;
	const HTTP_NOT_ACCEPTABLE = 406;
	const HTTP_PROXY_AUTHENTICATION_REQUIRED = 407;
	const HTTP_REQUEST_TIMEOUT = 408;
	const HTTP_CONFLICT = 409;
	const HTTP_GONE = 410;
	const HTTP_LENGTH_REQUIRED = 411;
	const HTTP_PRECONDITION_FAILED = 412;
	const HTTP_REQUEST_ENTITY_TOO_LARGE = 413;
	const HTTP_REQUEST_URI_TOO_LONG = 414;
	const HTTP_UNSUPPORTED_MEDIA_TYPE = 415;
	const HTTP_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
	const HTTP_EXPECTATION_FAILED = 417;
	// [Server Error 5xx]
	const HTTP_INTERNAL_SERVER_ERROR = 500;
	const HTTP_NOT_IMPLEMENTED = 501;
	const HTTP_BAD_GATEWAY = 502;
	const HTTP_SERVICE_UNAVAILABLE = 503;
	const HTTP_GATEWAY_TIMEOUT = 504;
	const HTTP_VERSION_NOT_SUPPORTED = 505;

	private static $messages = array(
		// [Informational 1xx]
		100=>'100 Continue',
		101=>'101 Switching Protocols',
		// [Successful 2xx]
		200=>'200 OK',
		201=>'201 Created',
		202=>'202 Accepted',
		203=>'203 Non-Authoritative Information',
		204=>'204 No Content',
		205=>'205 Reset Content',
		206=>'206 Partial Content',
		// [Redirection 3xx]
		300=>'300 Multiple Choices',
		301=>'301 Moved Permanently',
		302=>'302 Found',
		303=>'303 See Other',
		304=>'304 Not Modified',
		305=>'305 Use Proxy',
		306=>'306 (Unused)',
		307=>'307 Temporary Redirect',
		// [Client Error 4xx]
		400=>'400 Bad Request',
		401=>'401 Unauthorized',
		402=>'402 Payment Required',
		403=>'403 Forbidden',
		404=>'404 Not Found',
		405=>'405 Method Not Allowed',
		406=>'406 Not Acceptable',
		407=>'407 Proxy Authentication Required',
		408=>'408 Request Timeout',
		409=>'409 Conflict',
		410=>'410 Gone',
		411=>'411 Length Required',
		412=>'412 Precondition Failed',
		413=>'413 Request Entity Too Large',
		414=>'414 Request-URI Too Long',
		415=>'415 Unsupported Media Type',
		416=>'416 Requested Range Not Satisfiable',
		417=>'417 Expectation Failed',
		// [Server Error 5xx]
		500=>'500 Internal Server Error',
		501=>'501 Not Implemented',
		502=>'502 Bad Gateway',
		503=>'503 Service Unavailable',
		504=>'504 Gateway Timeout',
		505=>'505 HTTP Version Not Supported'
	);

	public static function httpHeaderFor($code) {
		return 'HTTP/1.1 ' . self::$messages[$code];
	}

	public static function getMessageForCode($code) {
		return self::$messages[$code];
	}

	public static function isError($code) {
		return is_numeric($code) && $code >= self::HTTP_BAD_REQUEST;
	}

	public static function canHaveBody($code) {
		return
			// True if not in 100s
			($code < self::HTTP_CONTINUE || $code >= self::HTTP_OK)
			&& // and not 204 NO CONTENT
			$code != self::HTTP_NO_CONTENT
			&& // and not 304 NOT MODIFIED
			$code != self::HTTP_NOT_MODIFIED;
	}
}
?>