PHP constants with descriptions of the most commonly used HTTP status codes

http_status_codes.php

<?php
declare(strict_types=1);

/**
 * Standard response for successful HTTP requests.
 * The actual response will depend on the request method used.
 * In a GET request, the response will contain an entity corresponding to the requested resource.
 * In a POST request, the response will contain an entity describing or containing the result of the action.
 */
define('HTTP_STATUS_OK', 200);

/**
 * The request has been fulfilled, resulting in the creation of a new resource.
 */
define('HTTP_STATUS_CREATED', 201);

/**
 * The request has been accepted for processing, but the processing has not been completed.
 * The request might or might not be eventually acted upon,
 * and may be disallowed when processing occurs.
 */
define('HTTP_STATUS_ACCEPTED', 202);

/**
 * The server successfully processed the request, and is not returning any content.
 */
define('HTTP_STATUS_NO_CONTENT', 204);

/**
 * The server is delivering only part of the resource due to a range header sent by the client.
 * The range header is used by HTTP clients to enable resuming of interrupted downloads,
 * or split a download into multiple simultaneous streams.
 */
define('HTTP_STATUS_PARTIAL_CONTENT', 206);

/**
 * This and all future requests should be directed to the given URI.
 */
define('HTTP_STATUS_MOVED_PERMANENTLY', 301);

/**
 * The response to the request can be found under another URI using the GET method.
 * When received in response to a POST (or PUT/DELETE),
 * the client should presume that the server has received the data
 * and should issue a new GET request to the given URI.
 */
define('HTTP_STATUS_SEE_OTHER', 303);

/**
 * Indicates that the resource has not been modified
 * since the version specified by the request headers If-Modified-Since or If-None-Match.
 * In such case, there is no need to retransmit the resource
 * since the client still has a previously-downloaded copy.
 */
define('HTTP_STATUS_NOT_MODIFIED', 304);

/**
 * The server cannot or will not process the request due to an apparent client error.
 */
define('HTTP_STATUS_BAD_REQUEST', 400);

/**
 * Specifically for use when authentication is required
 * and has failed or has not yet been provided.
 */
define('HTTP_STATUS_UNAUTHORIZED', 401);

/**
 * The request contained valid data and was understood by the server,
 * but the server is refusing action.
 * This may be due to the user not having the necessary permissions for a resource
 * or needing an account of some sort,
 * or attempting a prohibited action.
 * The request should not be repeated.
 */
define('HTTP_STATUS_FORBIDDEN', 403);

/**
 * The requested resource could not be found but may be available in the future.
 * Subsequent requests by the client are permissible.
 */
define('HTTP_STATUS_NOT_FOUND', 404);

/**
 * A request method is not supported for the requested resource;
 * for example, a GET request on a form that requires data to be presented via POST,
 * or a PUT request on a read-only resource.
 */
define('HTTP_STATUS_METHOD_NOT_ALLOWED', 405);

/**
 * The requested resource is capable of generating only content
 * not acceptable according to the Accept headers sent in the request.
 */
define('HTTP_STATUS_NOT_ACCEPTABLE', 406);

/**
 * The server timed out waiting for the request.
 * According to HTTP specifications: "The client did not produce a request
 * within the time that the server was prepared to wait.
 * The client may repeat the request without modifications at any later time.
 */
define('HTTP_STATUS_REQUEST_TIMEOUT', 408);

/**
 * Indicates that the request could not be processed because of conflict in the current state of the resource.
 */
define('HTTP_STATUS_CONFLICT', 409);

/**
 * The request is larger than the server is willing or able to process.
 */
define('HTTP_STATUS_PAYLOAD_TOO_LARGE', 413);

/**
 * The request entity has a media type which the server or resource does not support.
 */
define('HTTP_STATUS_UNSUPPORTED_MEDIA_TYPE', 415);

/**
 * The client has asked for a portion of the file,
 * but the server cannot supply that portion.
 */
define('HTTP_STATUS_RANGE_NOT_SATISFIABLE', 416);

/**
 * The RFC specifies this code should be returned by teapots requested to brew coffee.
 */
define('HTTP_STATUS_I_M_A_TEAPOT', 418);

/**
 * The request was well-formed but was unable to be followed due to semantic errors.
 */
define('HTTP_STATUS_UNPROCESSABLE_ENTITY', 422);

/**
 * A generic error message, given when an unexpected condition was
 * encountered and no more specific message is suitable.
 */
define('HTTP_STATUS_INTERNAL_SERVER_ERROR', 500);

/**
 * The server either does not recognize the request method,
 * or it lacks the ability to fulfil the request.
 */
define('HTTP_STATUS_NOT_IMPLEMENTED', 501);

/**
 * The server was acting as a gateway or proxy and
 * received an invalid response from the upstream server.
 */
define('HTTP_STATUS_BAD_GATEWAY', 502);

/**
 * The server cannot handle the request.
 */
define('HTTP_STATUS_SERVICE_UNAVAILABLE', 503);

/**
 * The server was acting as a gateway or proxy and
 * did not receive a timely response from the upstream server.
 */
define('HTTP_STATUS_GATEWAY_TIMEOUT', 504);

/**
 * The server does not support the HTTP protocol version used in the request.
 */
define('HTTP_STATUS_HTTP_VERSION_NOT_SUPPORTED', 505);