The document discusses REST (Representational State Transfer) and how to create a RESTful web service using PHP. It explains how to build a simple web service for a library that returns book price details. It includes code for functions.php to define the get_price() function, index.php to handle requests and return responses in JSON format, and request.php showing an example client request to the web service.

1. REST –Web Services

2. Web Basics: Retrieving Information using HTTP
GET
• The user types in at his browser: http://www.amazon.com
• - The browser software creates an HTTP header (no payload)
• - The HTTP header identifies:
• - The desired action: GET ("get me resource")
• - The target machine (www.amazon.com)
Amazon
Web Server
http://www.amazon.com
GET / HTTP/1.1
Host: http://www.amazon.com

3. Web Basics: Updating Information using HTTP
POST
• The user fills in the Web page's form
• The browser software creates an HTTP header with a payload
comprised of the form data. The HTTP header identifies:
The desired action: POST ("here's some update info")
The target machine (amazon.com)
The payload contains: The data being POSTed
Credit Card: Visa
Number: 123-45-6789
Expiry: 12-04-06
Credit Card: Visa
Number: 123-45-6789
Expiry: 12-04-06
Amazon
Web Server

4. What is REST?
• RESET stands for Representational state transfer
•" REST " was coined by Roy Fielding in his Ph.D. to describe a
design pattern for implementing networked systems.
• In the REST architectural style, data and functionality are
considered resources and are accessed usingUniform Resource
Identifiers (URIs), typically links on the Web.

5. Creating RESTful Web Service

6. Learn by example
• We are going to create a web service for a library -so that it will manage
request from clients and will respond with the details of the book
requested
• We will have the following files in our project (in www/library/)
– Functions.php // has an array of books and will return the price of book requested
– Index.php // will handle requests from clients and respond with data
– Request.php // will act as the client who request the data

7. <?php /* functions.php */
function get_price($find) {
$books = array('java'=>300,
'php'=>200,
'c'=>100);
foreach($books as $book=>$price) {
if($book==$find)
{
return $price;
break;
}
}
}
?>
Functions.php
• We have created a simple php
page named “function.php”
• Inside the page we have defined
a function named “get_price()”
that will accept book name as
argument and will return with its
price

8. Index.php
<?php
header("Content-Type:application/json");
include("functions.php");
if(!empty($_GET['name'])) {
$name = $_GET['name'];
$price = get_price($name);
if(empty($price))
deliver_response(200, "book not found", NULL);
else
deliver_response(200, "book found", $price);
}
Else {
deliver_response(400, "Invalid Request", NULL);
}

9. Creating RESTful Web Service
<?php
header("Content-Type:application/json");
include("functions.php");
if(!empty($_GET['name'])) {
$name = $_GET['name'];
$price = get_price($name);
if(empty($price))
deliver_response(200, "book not found",
NULL);
else
deliver_response(200, "book found", $price);
}
Else {
deliver_response(400, "Invalid Request",
NULL);
}
Created a header mentioning the
response will be in json format

10. Creating RESTful Web Service
<?php
header("Content-Type:application/json");
include("functions.php");
if(!empty($_GET['name'])) {
$name = $_GET['name'];
$price = get_price($name);
if(empty($price))
deliver_response(200, "book not found",
NULL);
else
deliver_response(200, "book found", $price);
}
Else {
deliver_response(400, "Invalid Request",
NULL);
}
Including the page functions.php
that we have created earlier

11. Creating RESTful Web Service
<?php
header("Content-Type:application/json");
include("functions.php");
if(!empty($_GET['name'])) {
$name = $_GET['name'];
$price = get_price($name);
if(empty($price))
deliver_response(200, "book not found",
NULL);
else
deliver_response(200, "book found", $price);
}
Else {
deliver_response(400, "Invalid Request",
NULL);
}
Checking whether the URL request
contains the name of book or not?
If the URL request doesn’t have the
book name returns error message

12. Creating RESTful Web Service
<?php
header("Content-Type:application/json");
include("functions.php");
if(!empty($_GET['name'])) {
$name = $_GET['name'];
$price = get_price($name);
if(empty($price))
deliver_response(200, "book not found",
NULL);
else
deliver_response(200, "book found", $price);
}
Else {
deliver_response(400, "Invalid Request",
NULL);
}
Accepting the argument into a
variable named “$name”

13. Creating RESTful Web Service
<?php
header("Content-Type:application/json");
include("functions.php");
if(!empty($_GET['name'])) {
$name = $_GET['name'];
$price = get_price($name);
if(empty($price))
deliver_response(200, "book not found",
NULL);
else
deliver_response(200, "book found", $price);
}
Else {
deliver_response(400, "Invalid Request",
NULL);
}
Calling the function get_price() with
the book name and stores the price
returned in a varaible named $price

14. Creating RESTful Web Service
<?php
header("Content-Type:application/json");
include("functions.php");
if(!empty($_GET['name'])) {
$name = $_GET['name'];
$price = get_price($name);
if(empty($price))
deliver_response(200, "book not found",
NULL);
else
deliver_response(200, "book found", $price);
}
Else {
deliver_response(400, "Invalid Request",
NULL);
}
If the price is empty – calls a
function named deliver_response
with the “book not found”
arguments

15. Creating RESTful Web Service
<?php
header("Content-Type:application/json");
include("functions.php");
if(!empty($_GET['name'])) {
$name = $_GET['name'];
$price = get_price($name);
if(empty($price))
deliver_response(200, "book not found",
NULL);
else
deliver_response(200, "book found", $price);
}
Else {
deliver_response(400, "Invalid Request",
NULL);
}
If the price is not empty – call the
same method deliver_response
with “book found ” arguments

16. Creating RESTful Web Service
function deliver_response($status,$status_message,$data)
{
header("HTTP/1.1 $status $status_message");
$response['status']=$status;
$response['status_message']=$status_message;
$response['data']=$data;
$json_response = json_encode($response);
echo $json_response;
}
?>
Sets the header witht the
status code and message

17. Creating RESTful Web Service
function deliver_response($status,$status_message,$data)
{
header("HTTP/1.1 $status $status_message");
$response['status']=$status;
$response['status_message']=$status_message;
$response['data']=$data;
$json_response = json_encode($response);
echo $json_response;
}
?>
Creates an array of status,
messafe and the data(ie
price of book)

18. Creating RESTful Web Service
function deliver_response($status,$status_message,$data)
{
header("HTTP/1.1 $status $status_message");
$response['status']=$status;
$response['status_message']=$status_message;
$response['data']=$data;
$json_response = json_encode($response);
echo $json_response;
}
?>
Create a json object using
an inbuilt function in php
named json_encode() and
passing the array we just
created as argument

19. Creating RESTful Web Service
function deliver_response($status,$status_message,$data)
{
header("HTTP/1.1 $status $status_message");
$response['status']=$status;
$response['status_message']=$status_message;
$response['data']=$data;
$json_response = json_encode($response);
echo $json_response;
}
?>
Echo the json object so
that any clients request
the book will be get the
details as a json object

20. How to call a Web Service – request.php
<?php
$url= 'http://127.1.1.0/library/?name=php';
$response = file_get_contents($url);
$data = json_decode($response, true);
var_dump($data);
?>
Creates a url to which we pass an
argument name=php

21. How to call a Web Service – request.php
<?php
$url= 'http://127.1.1.0/library/?name=php';
$response = file_get_contents($url);
$data = json_decode($response, true);
var_dump($data);
?>
Makes the request with the url we
created and stores the result in a
variable named $response(obviously
the result will be returned in json
format)

22. How to call a Web Service – request.php
<?php
$url= 'http://127.1.1.0/library/?name=php';
$response = file_get_contents($url);
$data = json_decode($response, true);
var_dump($data);
?>
Decodes the json result into array
format and displays it on the screen

23. Questions?
“A good question deserve a good grade…”

24. Self Check !!

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