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200, 404, 302. Is it a lock combination? A phone number? No, they're HTTP status codes! As we develop Web applications, we encounter these status codes and others, and often we make decisions about which ones to return without giving much thought to their meaning or context. It's time to take a deeper look at HTTP. Knowing the methods, headers, and status codes, what they mean, and how to use them can help you develop richer Internet applications. Join Ben Ramsey as he takes you on a journey through RFC 2616 to discover some of the gems of HTTP.
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Making the Most of HTTP In Your Apps
Ben Ramsey • Dutch PHP Conference22 May 2009
Why HTTP?
Because you are a Web developer.
HTTP is the Web.
That’s all I have to say about that.
Some properties of HTTP...
❖ A client-server architecture
❖ Atomic
❖ Cacheable
❖ A uniform interface
❖ Layered
❖ Code on demand
Now, what does that sound like?
REST!
And, that’s all I have to say about that, too.
Our focus today...
❖ Methods
❖ Status Codes
❖ Playing with raw HTTP
❖ HTTP in PHP
Defining safe & idempotentmethods
Safe methods
❖ GET & HEAD should not take action other than retrieval
❖ These are considered safe
❖ Allows agents to represent POST, PUT, & DELETE in a special way
Idempotence
❖ Side-effects of N > 0 identical requests is the same as for a single request
❖ GET, HEAD, PUT and DELETE share this property
❖ OPTIONS and TRACE are inherently idempotent
Methods
❖ Retrieval of information
❖ Transfers a representation of a resource from the server to the client
❖ Safe
❖ Idempotent
GET
HEAD
❖ Identical to GET, except...
❖ Returns only the headers, not the body
❖ Useful for getting details about a resource representation before retrieving the full representation
❖ Safe
❖ Idempotent
POST
❖ The body content should be accepted as a new subordinate of the resource
❖ Append, annotate, paste after
❖ Not safe
❖ Non-idempotent
PUT
❖ Opposite of GET
❖ Storage of information
❖ Transfers a representation of a resource from the client to the server
❖ Not safe
❖ Idempotent
DELETE
❖ Requests that the resource identified be removed from public access
❖ Not safe
❖ Idempotent
Other methods
❖ OPTIONS
❖ TRACE
❖ CONNECT
Status codes
❖ Informational (1xx)
❖ Successful (2xx)
❖ Redirection (3xx)
❖ Client error (4xx)
❖ Server error (5xx)
Informational (1xx)
100 Continue
1. Client sends a request without a body and includes the Expect: 100-continue header and all other headers
2. Server determines whether it will accept the request and responds with 100 Continue (or a 4xx code on error)
3. Client sends the request again with the body and without the Expect header
1
POST /content/videos HTTP/1.1Host: example.orgContent-Type: video/mp4Content-Length: 115910000Authorization: Basic bWFkZTp5b3VfbG9vaw==Expect: 100-continue
2
HTTP/1.1 413 Request Entity Too LargeDate: Thu, 21 May 2009 23:05:15 GMTServer: Apache/2.2.11 (Unix) DAV/2 PHP/5.3.0RC2X-Powered-By: PHP/5.3.0RC2Content-Length: 0Connection: closeContent-Type: text/html
Failure state
2
HTTP/1.1 100 ContinueDate: Thu, 21 May 2009 23:05:15 GMTServer: Apache/2.2.11 (Unix) DAV/2 PHP/5.3.0RC2X-Powered-By: PHP/5.3.0RC2Content-Length: 0Content-Type: text/html
Success state
3
POST /content/videos HTTP/1.1Host: example.orgContent-Type: video/mp4Content-Length: 115910000Authorization: Basic bWFkZTp5b3VfbG9vaw==
{binary video data}
4
HTTP/1.1 201 CreatedDate: Thu, 21 May 2009 23:05:34 GMTServer: Apache/2.2.11 (Unix) DAV/2 PHP/5.3.0RC2X-Powered-By: PHP/5.3.0RC2Content-Length: 119Content-Type: text/htmlLocation: http://example.org/content/videos/1234
<html><body><p>Video uploaded! Go <a href="http://example.org/content/videos/1234">here</a> to see it.</p></body></html>
Successful (2xx)
200 OKGET /content/videos/1234 HTTP/1.1Host: example.org
HTTP/1.x 200 OKDate: Thu, 21 May 2009 23:08:35 GMTServer: Apache/2.2.11 (Unix) DAV/2 PHP/5.3.0RC2X-Powered-By: PHP/5.3.0RC2Content-Type: video/mp4Content-Length: 115910000
{binary data}
201 Created
1
POST /content/videos HTTP/1.1Host: example.orgContent-Type: video/mp4Content-Length: 115910000Authorization: Basic bWFkZTp5b3VfbG9vaw==
{binary video data}
201 Created
2
HTTP/1.x 201 CreatedDate: Thu, 21 May 2009 23:05:34 GMTServer: Apache/2.2.11 (Unix) DAV/2 PHP/5.3.0RC2X-Powered-By: PHP/5.3.0RC2Content-Length: 120Content-Type: text/htmlLocation: http://example.org/content/videos/1234
<html><body><p>Video uploaded! Go <a href="http://example.org/content/videos/1234">here</a> to see it.</p></body></html>
202 Accepted
2
HTTP/1.x 202 AcceptedDate: Thu, 21 May 2009 23:05:34 GMTServer: Apache/2.2.11 (Unix) DAV/2 PHP/5.3.0RC2X-Powered-By: PHP/5.3.0RC2Content-Length: 137Content-Type: text/htmlLocation: http://example.org/content/videos/1234/status
<html><body><p>Video processing! Check <a href="http://example.org/content/videos/1234/status">here</a> for the status.</p></body></html>
204 No Content
1
DELETE /content/videos/1234 HTTP/1.1Host: example.orgAuthorization: Basic bWFkZTp5b3VfbG9vaw==
204 No Content
2
HTTP/1.x 204 No ContentDate: Thu, 21 May 2009 23:28:34 GMT
205 Reset Content
“The server has fulfilled the request and the user agent SHOULD reset the document view which caused the request to be sent. This response is primarily intended to allow input for actions to take place via user input, followed by a clearing of the form in which the input is given so that the user can easily initiate another input action.”
206 Partial Content
❖ Used when requests are made for ranges of bytes from a resource
❖ Determine whether a server supports range requests by checking for the Accept-Ranges header with HEAD
1
HEAD /2390/2253727548_a413c88ab3_s.jpg HTTP/1.1Host: farm3.static.flickr.com
2
HTTP/1.0 200 OKDate: Mon, 05 May 2008 00:33:14 GMTServer: Apache/2.0.52 (Red Hat)Accept-Ranges: bytesContent-Length: 3980Content-Type: image/jpeg
3
GET /2390/2253727548_a413c88ab3_s.jpg HTTP/1.1Host: farm3.static.flickr.comRange: bytes=0-999
4
HTTP/1.0 206 Partial ContentDate: Mon, 05 May 2008 00:36:57 GMTServer: Apache/2.0.52 (Red Hat)Accept-Ranges: bytesContent-Length: 1000Content-Range: bytes 0-999/3980Content-Type: image/jpeg
{binary data}
Redirection (3xx)
303 See Other
❖ The response to your request can be found at another URL identified by the Location header
❖ The client should make a GET request on that URL
❖ The Location is not a substitute for this URL
307 Temporary Redirect❖ The resource resides temporarily at the
URL identified by the Location
❖ The Location may change, so don’t update your links
❖ If the request is not GET or HEAD, then you must allow the user to confirm the action
302 Found
❖ The resource has been found at another URL identified by the Location header
❖ The new URL might be temporary, so the client should continue to use this URL
❖ Redirections SHOULD be confirmed by the user (in practice, browsers don’t respect this)
301 Moved Permanently
❖ The resource has moved permanently to the URL indicated by the Location header
❖ You should update your links accordingly
❖ Great for forcing search engines, etc. to index the new URL instead of this one
Client error (4xx)
❖ 400 Bad Request
❖ 401 Unauthorized / 403 Forbidden
❖ 404 Not Found
❖ 405 Method Not Allowed
❖ 410 Gone
❖ 411 Length Required
❖ 413 Request Entity Too Large
❖ 415 Unsupported Media Type
❖ 416 Requested Range Not Satisfiable
Server error (5xx)
❖ 500 Internal Server Error
❖ 503 Service Unavailable
Manipulating raw HTTP
[bramsey@pippin ~] telnet phparch.com 80
[bramsey@pippin ~] telnet phparch.com 80Trying 64.34.173.96...Connected to phparch.com.Escape character is '^]'.
[bramsey@pippin ~] telnet phparch.com 80Trying 64.34.173.96...Connected to phparch.com.Escape character is '^]'.HEAD / HTTP/1.1Host: phparch.com
[bramsey@pippin ~] telnet phparch.com 80Trying 64.34.173.96...Connected to phparch.com.Escape character is '^]'.HEAD / HTTP/1.1Host: phparch.com
HTTP/1.1 200 OKDate: Thu, 21 May 2009 21:01:06 GMTServer: Apache/2.2.9 (Debian) PHP/5.2.5 mod_ssl/2.2.9 OpenSSL/0.9.8gX-Powered-By: PHP/5.2.5Set-Cookie: PHPSESSID=eeeff50d3b6ae241c934a5c2671b0005; expires=Sun, 21 Jun 2009 21:01:07 GMT; path=/; domain=.phparch.comExpires: Thu, 19 Nov 1981 08:52:00 GMTCache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0Pragma: no-cacheContent-Type: text/html; charset=utf-8
Connection closed by foreign host.
Using HTTP in PHP
❖ header() functionhttp://php.net/header
❖ Client URL library (cURL)http://php.net/curl
❖ Streamshttp://php.net/streams
❖ HTTP extension (pecl/http)http://php.net/http
header() example
<?php
header('HTTP/1.x 201 Created');header('Content-Type: application/xml');header('Location: http://example.org/content/videos/1234');
echo $htmlBody;
?>
HTTP/1.1 201 CreatedDate: Fri, 12 Jun 2009 13:53:38 GMTServer: Apache/2.2.11 (Unix) DAV/2 PHP/5.3.0RC2X-Powered-By: PHP/5.3.0RC2Location: http://example.org/content/videos/1234Content-Length: 120Content-Type: text/html
<html><body><p>Video uploaded! Go <a href="http://example.org/content/videos/1234">here</a> to see it.</p></body></html>
cURL example
// Send a DM to a Twitter friend$dm = array( 'user' => 'ramsey', 'text' => 'Hi! I\'m using your curl code!');
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, "http://twitter.com/direct_messages/new.json");curl_setopt($curl, CURLOPT_POST, true);curl_setopt($curl, CURLOPT_POSTFIELDS, $dm);curl_setopt($curl, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);curl_setopt($curl, CURLOPT_USERPWD, "{$username}:{$password}");curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
// Suppress the Expect: 100-continue header that // cURL tries to sendcurl_setopt($curl, CURLOPT_HTTPHEADER, array('Expect:'));
$response = curl_exec($curl);curl_close($curl);
{"text":"Hi! I'm using your curl code!","sender":{"notifications":false,"profile_text_color":"333333","profile_image_url":"http:\/\/s3.amazonaws.com\/twitter_production\/profile_images\/66941217\/phpc_normal.png","description":"PHPC is a gathering place for the PHP community. It is about community and friendship.","profile_background_image_url":"http:\/\/s3.amazonaws.com\/twitter_production\/profile_background_images\/3561102\/php2.png","utc_offset":-18000,"time_zone":"Eastern Time (US & Canada)","created_at":"Tue Dec 09 18:05:32 +0000 2008","profile_link_color":"333366","screen_name":"phpc","profile_background_tile":false,"followers_count":2163,"profile_background_color":"000000","url":"http:\/\/phpcommunity.org\/","name":"PHP Community","friends_count":2146,"protected":false,"statuses_count":213,"profile_sidebar_fill_color":"d4d5e8","profile_sidebar_border_color":"333333","following":false,"favourites_count":0,"location":"#phpc on Freenode IRC","id":17997273,"verified_profile":false},"created_at":"Fri Jun 12 14:08:34 +0000 2009","sender_id":17997273,"sender_screen_name":"phpc","recipient_screen_name":"ramsey","recipient_id":7794552,"id":170497722,"recipient":{"notifications":false,"profile_text_color":"000000","profile_image_url":"http:\/\/s3.amazonaws.com\/twitter_production\/profile_images\/81619004\/bramsey-square_normal.png","description":"Dad, Software Architect, PHP, XML, web services, beer drinker, libertarian","profile_background_image_url":"http:\/\/static.twitter.com\/images\/themes\/theme1\/bg.gif","utc_offset":-18000,"time_zone":"Eastern Time (US & Canada)","created_at":"Sun Jul 29 02:44:40 +0000 2007","profile_link_color":"0066CC","screen_name":"ramsey","profile_background_tile":false,"followers_count":817,"profile_background_color":"666666","url":"http:\/\/benramsey.com\/","name":"Ben Ramsey","friends_count":187,"protected":false,"statuses_count":5062,"profile_sidebar_fill_color":"99ff66","profile_sidebar_border_color":"33cc00","following":0,"favourites_count":23,"location":"Atlanta, GA, US","id":7794552,"verified_profile":false}}
Questions?
❖ My website is benramsey.com
❖ Rate this talk at joind.in/576
❖ Read the HTTP spec attools.ietf.org/html/rfc2616
❖ My company is Schematicschematic.com
Making the Most of HTTP In Your AppsCopyright © Ben Ramsey. Some rights reserved.
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
For uses not covered under this license, please contact the author.
