Working with web_services

Who am I?

• Lorna Mitchell
• PHP Specialist
• Developer, Writer, Consultant, Trainer
• Personal site at lornajane.net
• Twitter: @lornajane
• PHPNW, PHPWomen

2

Working with Web Services

• Consuming existing services
• Web services overview
• Data types
• Service types
• Debugging
• Using services from PHP

3

What are Web Services?

• Machine-friendly applications
• Formatted data instead of a web page

4

Why Do We Care?

• Web services let us exchange data
– between systems
– within systems
• Architecture looks like library or
module boundary
• Sharing information between systems
cleanly

5

How do Web Services Work?

• Client/Server
• Sound familiar?
• Request and response, just like a web
application
• Same theories apply

6

When Things Go Wrong

• Errors will appear in response
• We may not expect them
• Apache logs
• Debug output and logging
• Verbose error-checking and logging
from our app
• Graceful failure

7

JSON

• JavaScript Object Notation
• Natively read/write in most languages
• Very simple! (we like simple)
• Limitations
– no data typing
– no distinction between object and array

9

Writing JSON from PHP
1 <?php
2
3 $menu['starter'] = array( "prawn cocktail",
4 "soup of the day");
5 $menu['main course'] = array( "roast chicken",
6 "fish 'n' chips",
7 "macaroni cheese");
8 $menu['pudding'] = array( "cheesecake",
9 "treacle sponge");
10
11 echo json_encode($menu);

{"starter":["prawn cocktail","soup of the day"],"main
course":["roast chicken","fish 'n' chips","macaroni
cheese"],"pudding":["cheesecake","treacle sponge"]}
10

Reading JSON from PHP
1 <?php
2
3 $json = '{"starter":["prawn cocktail","soup of the
day"],"main course":["roast chicken","fish 'n'
chips","macaroni cheese"],"pudding":["cheesecake","treacle
sponge"]}';
4
5 print_r(json_decode($json));

11

Reading JSON from PHP
stdClass Object
(
[starter] => Array
(
[0] => prawn cocktail
[1] => soup of the day
)

[main course] => Array
(
[0] => roast chicken
[1] => fish 'n' chips
[2] => macaroni cheese
)

[pudding] => Array
(
[0] => cheesecake
[1] => treacle sponge
)
12
)

XML

• eXtensible Markup Language
• Familiar
• Can give more detail than JSON
• Native read/write in most languages

13

Working with XML from PHP

• Lots of options
• SimpleXML
• DOM

14

SimpleXML Example
1 <?php
2
3 $xml = <<< XML
4 <?xml version="1.0" ?>
5 <menus>
6 <menu>Lunch</menu>
7 <menu>Dinner</menu>
8 <menu>Dessert</menu>
9 <menu>Drinks</menu>
10 </menus>
11 XML;
12
13 $simplexml = new SimpleXMLElement($xml);
14 var_dump($simplexml);

15

SimpleXML Example
object(SimpleXMLElement)#1 (1) {
["menu"]=>
array(5) {
[0]=>
string(5) "Lunch"
[1]=>
string(6) "Dinner"
[2]=>
string(7) "Dessert"
[3]=>
string(6) "Drinks"
}
}

16

SimpleXML Example
1 <?php
2
3 $simplexml = simplexml_load_string('<?xml
version="1.0" ?><menus/>');
4 $simplexml->addChild('menu','Lunch');
5 $simplexml->addChild('menu','Dinner');
6 $simplexml->addChild('menu','Drinks');
7 $simplexml->addChild('menu','Dessert');
8
9 echo $simplexml->asXML();

17

SimpleXML Example
<?xml version="1.0"?>
<menus>
<menu>Lunch</menu>
<menu>Dinner</menu>
<menu>Dessert</menu>
<menu>Drinks</menu>
</menus>

18

Serialised PHP

• Native to PHP
• Useful for values in database
• Can also use to move data between
PHP applications

19

Serialising Data in PHP
1 <?php
2
3 $menu['starter'] = array( "prawn cocktail",
4 "soup of the day");
5 $menu['main course'] = array( "roast chicken",
6 "fish 'n' chips",
7 "macaroni cheese");
8 $menu['pudding'] = array( "cheesecake",
9 "treacle sponge");
10
11 echo serialize($menu);

a:3:{s:7:"starter";a:2:{i:0;s:14:"prawn
cocktail";i:1;s:15:"soup of the day";}s:11:"main
course";a:3:{i:0;s:13:"roast chicken";i:1;s:14:"fish'n'
chips";i:2;s:15:"macaroni cheese";}s:7:"pudding";a:2:
{i:0;s:10:"cheesecake";i:1;s:14:"treacle sponge";}}
20

Unserialising Data in PHP
1 <?php
2
3 $serialised = 'a:3:{s:7:"starter";a:2:{i:0;s:14:"prawn
cocktail";i:1;s:15:"soup of the day";}s:11:"main
course";a:3:{i:0;s:13:"roast chicken";i:1;s:14:"fish 'n'
chips";i:2;s:15:"macaroni cheese";}s:7:"pudding";a:2:
{i:0;s:10:"cheesecake";i:1;s:14:"treacle sponge";}}';
4
5 var_dump(unserialize($serialised));

21

Unserialising Data in PHP
array(3) {
["starter"]=>
array(2) {
[0]=>
string(14) "prawn cocktail"
[1]=>
string(15) "soup of the day"
}
["main course"]=>
array(3) {
[0]=>
string(13) "roast chicken"
[1]=>
string(14) "fish 'n' chips"
[2]=>
string(15) "macaroni cheese"
}
["pudding"]=>
array(2) {
[0]=>
string(10) "cheesecake"
[1]=>
string(14) "treacle sponge"
} 22
}

Service Types

• SOAP
• *-RPC
– XML-RPC
– JSON-RPC
• REST

24

SOAP

• Just "soap"
• Defined XML format
• Also includes definition for error format
• Wrappers available for most languages
• Optionally uses a WSDL to describe the
service
– Web Service Description Language

25

Example WSDL
<?xml version ='1.0' encoding ='UTF-8' ?>
<definitions name='MyClass' targetNamespace='urn:MyClassInventory' xmlns:tns='urn:MyClassInventory' xmlns:soap='http://schemas.xmlsoap.org/wsdl/soap/' xmlns:xsd='
http://www.w3.org/2001/XMLSchema' xmlns:soapenc='http://schemas.xmlsoap.org/soap/encoding/' xmlns:wsdl='http://schemas.xmlsoap.org/wsdl/'
xmlns='http://schemas.xmlsoap.org/wsdl/'>
<message name='getAccountStatusRequest'>
<part name='accountID' type='xsd:string'/>
</message>
<message name='getAccountStatusResponse'>
<part name='accountID' type='xsd:string'/>
<part name='counter' type='xsd:float' />
</message>
<portType name='MyClassPortType'>
<operation name='getAccountStatus'>
<input message='tns:getAccountStatusRequest'/>
<output message='tns:getAccountStatusResponse'/>
</operation>
</portType>
<binding name='MyClassBinding' type='tns:MyClassPortType'>
<soap:binding style='rpc'
transport='http://schemas.xmlsoap.org/soap/http'/>
<operation name='getAccountStatus'>
<soap:operation soapAction='urn:xmethods-delayed-quotes#getAccountStatus'/>
<input>
<soap:body use='encoded' namespace='urn:xmethods-delayed-quotes' encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'/>
</input>
<output>
<soap:body use='encoded' namespace='urn:xmethods-delayed-quotes'
encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'/>
</output>
</operation>
</binding>
<service name='MyClassService'>
<port name='MyClassPort' binding='tns:MyClassBinding'>
<soap:address location='http://rivendell.local:10002/MyClassServiceServer.php'/>
</port>
</service>
</definitions>

26

WSDL tips

• Read from end to beginning
1.Service location and name
2.Method names and bindings
3.Details of request/response messages
4.Variable names and data types used for
each request/response
5.Data type definitions
6.Namespace information

27

PHP SOAP Client Example
1 <?php
2
3 ini_set('soap.wsdl_cache_enabled','0');
4
5 require_once('lib/Snapshot.php');
6
7 $wsdl = "Service.wsdl";
8 $client = new SoapClient($wsdl, $params);
9
10 $output = $client->requestShot(
11 'http://www.php.net','', 300, 400);

28

Troubleshooting SOAP

• Check request
– $client->getLastRequest()
• Check request headers
– $client->getLastRequestHeaders()
• Check WSDL
• Data types can be an issue between
different client/server languages

29

HTTP Debugging Tools

• cURL
– http://curl.haxx.se/
• Wireshark
– http://www.wireshark.org/
• Charles
– http://www.charlesproxy.com/

30

cURL

• cURL is a command-line tool
• Simple but powerful
• Specify HTTP verb
• Observe full request/response headers
• Handle cookies

31

cURL Cheat Sheet

• curl http://localhost
• -v to show request/response
• -I to show response headers
• -X to specify HTTP method
• -d to add a data field
• -c to store cookies in a cookiejar
• -b to use a cookiejar with request

32

Wireshark Examples

33

Wireshark Examples

34

Wireshark Examples

35

Wireshark Examples

36

RPC Services

• Remote Procedure Call
• Similar to library
• Call function with arguments

37

Example RPC services

• Using Flickr's XML-RPC
• Test method: just echoes back to user
• XML formatted data

38

Flickr Echo Example: XML
<?xml version="1.0"?>
<methodCall>
<methodName>flickr.test.echo</methodName>
<params>
<param>
<value>
<struct>
<member>
<name>api_key</name>
<value>....</value>
</member>
</struct>
</value>
</param>
</params>
</methodCall>

39

RPC from PHP: curl
1 <?php
2
3 // $xml is existing SimpleXMLElement Object
4 $url = 'http://api.flickr.com/services/xmlrpc/';
5 $ch = curl_init($url);
6
7 curl_setopt($ch, CURLOPT_POST, 1);
8 curl_setopt($ch, CURLOPT_POSTFIELDS, $xml->asXML());
9
10 $response = curl_exec($ch);
11 curl_close($ch);

40

RPC from PHP: pecl_http
1 <?php
2
3 $url = 'http://api.flickr.com/services/xmlrpc/';
4
5 // procedural method
6 $response = http_post_data($url, $xml->asXML());
7
8 // alternative method
9 $request = new HTTPRequest($url, HTTP_METH_POST);
10 $request->setRawPostData($xml->asXML());
11 $request->send();
12 $response = $request->getResponseBody();
13
14 var_dump($response);

41

Flickr Response
<?xml version="1.0" encoding="utf-8" ?>
<methodResponse>
<params>
<param>
<value>
<string><api_key>54rt346</api_key>
</string>
</value>
</param>
</params>
</methodResponse>

42

Wrapping RPC

• RPC is a library-like interface
• Can easily wrap existing libraries to
call like this
• Can wrap an interface to an RPC
service to look like a library

43

Wrapping RPC Example
1 <?php
2
3 class Handler
4 {
5 function __call($method, $args) {
6 $ch = curl_init('http://localhost');
7 $data['method'] = $method;
8 foreach($args as $a) $data[$a] = $a;
9
10 curl_setopt($ch, CURLOPT_POST,1);
11 curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
12 $response = curl_exec($ch); curl_close($ch);
13
14 var_dump($response);
15 }
16 }
17 $h = new Handler();
18 $h->dance('cat','dog','rabbit','penguin'); 44
19

Troubleshooting RPC

• Break down into smallest steps
• Can you get a response from the
service?
• Can you log in?
• Is there an error?
• Try to debug the details of the
request/response

45

REST

• REpresentational State Transfer
• Not a protocol
• More like a philosophy

46

REST Overview

• A series of concepts
• Generally uses HTTP (HyperText
Transfer Protocol)
• URLs are resource locations
• Verbs tell the service what to do
• Status codes indicate what the
outcome was

47

HTTP Status Codes

Code Meaning
200 OK
302 Found
301 Moved
401 Not Authorised
403 Forbidden
404 Not Found
500 Internal Server Error
48

REST CRUD

Action HTTP Verb

Retrieve GET

Create POST

Update PUT

Delete DELETE

49

REST Examples

• GET
– http://localhost/users
– http://localhost/users/harry
• POST
– http://localhost/users
• PUT
• DELETE
50

REST from PHP: GET
1 <?php
2
3 $result = file_get_contents('http://localhost/users');
4 var_dump($result);

51

REST from PHP: GET
1 <?php
2
3 $ch = curl_init('http://localhost/users');
4
5 curl_exec($ch);

• Health Warning!
– curl will echo output
– use CURLOPT_RETURNTRANSFER to
capture it instead

52

REST from PHP: POST
1 <?php
2
3 $ch = curl_init('http://localhost/users');
4
5 $data = array ("name" => "Cho Chang",
6 "house" => "Ravenclaw");
7
8 curl_setopt($ch, CURLOPT_POST, 1);
10
11 curl_exec($ch);

53

REST from PHP: DELETE
1 <?php
2
3 $ch = curl_init('http://localhost/users/ginny');
4
5 curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'DELETE');
6
7 curl_exec($ch);

54

REST from PHP: PUT
1 <?php
2
3 $ch = curl_init('http://localhost/users/cho');
4
5 $data = array ("name" => "Cho Chang",
6 "house" => "Ravenclaw"
7 "age" => 15);
8
9 curl_setopt($handle, CURLOPT_CUSTOMREQUEST, 'PUT');
11
12 curl_exec($ch);
13

55

Troubleshooting REST

• Does resource exist?
• Is there a status code?
• What does the response body look
like?
• Intercept web traffic
• Use command line curl

56

Working with Web Services

• Consuming existing services
• Web services overview
• Data types
• Service types
• Debugging
• Using services from PHP

58

Top tips

• If your app can't talk to the service,
can you get closer to the service?
• If you control both server and client,
add debug output
• Use proxies to record what happens
• Start with the lowest common
denominator and work up

59

Thankyou!

Twitter: @lornajane
Website: http://lornajane.net

Working with web_services

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