Building HTTP clients in PHP. A PHP package for sending HTTP requests and getting responses A PHP...

Building HTTP clients in PHP

A PHP package for sending HTTP requests and getting responses

• A PHP package for handling HTTP requests/responses is available

• It is called HTTP_Request

and is part of the PEAR repository of PHP extensions and applications -- see http://pear.php.net/

• The HTTP_Request documentation is here: http://pear.php.net/manual/en/package.http.http-request.php

• PEAR uses the object-oriented programming paradigm which is supported by PHP

• Before looking at HTTP_Request, we will review a few details of OOP in PHP

OOP in PHP (contd.)

• The object model in PHP was rewritten for PHP 5

• The PHP manual contains two main section on OOP:– Chapter 18. Classes and Objects (PHP 4)– Chapter 19. Classes and Objects (PHP 5)

• A full treatment of OOP in PHP is beyond our scope here

Object-oriented programming in PHP• Example class and its usage

<?php

class widget

{

var $x;

function say_hello() {echo "Hello, World!";}

function set_x($value) {$this->x = $value;}

function get_x() {return $this->x;}

}

$thing1 =& new widget;

$thing1->say_hello();

$thing1->set_x(98);

$y = $thing1->get_x();

echo " y is $y";

?>

Example HTTP client program in PHP<?php

require_once "HTTP/Request.php";

$req = & new HTTP_Request('http://www.rte.ie/');

if (!PEAR::isError($req->sendRequest()))

{

$contents= $req->getResponseBody();

echo $contents;

}

?>

• Note we have not handled fact that some URLs on RTE site are relative

• Thus, output (top image) not quite right; should be as in bottom inage

HTTP_Request package

• We will now examine details of the HTTP_Request package

• Information on the package is here:http://pear.php.net/package/HTTP_Request/docs/

• Some end-user documentation is available here:

http://pear.php.net/manual/en/package.http.http-request.php

HTTP_Request methods• Current description of the HTTP_Request class is here:http://pear.php.net/package/HTTP_Request/docs/latest/apidoc/HTTP_Request-1.2.4/HTTP_Request.html

(This may become outdated as new versions of the class are produced)

• The list of methods provided by the class appears to beHTTP_Request

setMethod setURL setHttpVer

addHeader addCookie removeHeader

addQueryString addRawQueryString

addPostData addRawPostData addFile

setBasicAuth setProxy

sendRequest

getResponseCode getResponseHeader getResponseCookies

getResponseBody

HTTP_Request (contd.)

• The set of methods provided by HTTP_Request corresponds to the structure of requests and responses defined in the HTTP protocol

Structure of HTTP requests/responses

• Requests: a three-part structure

request line

(Method URL[+query] HTTP-version)

headers

body• Responses: also a three-part structure

status line

(HTTP-version NatLangPhrase Response-Code)

headers

body

Structure of HTTP requests and corresponding HTTP_Request methods

• Request structurerequest line

(Method URL[+query] HTTP-version)

headers

body

• HTTP_Request methods• Methods for manipulating the Request Line setMethod setURL setHttpVer

addQueryString addRawQueryString

• Methods for manipulating the Headers addHeader addCookie removeHeader

• Methods for manipulating the body addPostData addRawPostData addFile

cs 4408 got here on 1 nov 2005/

Structure of HTTP responses and corresponding HTTP_Request methods

• Response structurestatus line

(HTTP-version NatLangPhrase Response-Code)

headers

body

• HTTP_Request methods• Methods for reading the status line getResponseCode

• Methods for reading the Headers getResponseHeader getResponseCookies

• Methods for reading the body getResponseBody

Creating a request object• Method for creating a request object

HTTP_Request

Format of call:

HTTP_Request HTTP_Request( $url $url [,array() $params]) • Params is asssociative array which can include:– method - Method to use, GET, POST etc – http - HTTP Version to use, 1.0 or 1.1 – user - Basic Auth username – pass - Basic Auth password – proxy_host - Proxy server host – proxy_port - Proxy server port – proxy_user - Proxy auth username – proxy_pass - Proxy auth password

– timeout - Connection timeout in seconds.

Creating a request object (contd.)

• Example usages of method for creating a request object $req =& new HTTP_Request();

$req =& new HTTP_Request("http://www.rte.ie/");

$req =& new HTTP_Request("http://www.rte.ie/",

array(method=>'GET',http=>'1.1'));

• In the first example, no aspect of the new request is specified; they can all be specified later, using other methods, before the request is sent to the server

• In the second example, the URL is specified; other aspects can be specified later, using other methods

• In the third example, the method, the URL and the HTTP version are specified; other aspects can be specified later, using other methods

Sending a request object• Method for sending a request object

sendRequest

Format of call:mixed sendRequest()

• Method returns:– a PEAR error message if there is an error,

– true otherwise • Example usage of method for creating a request object• Example 1:

$request =& new HTTP_Request("http://www.rte.ie/");

$request->sendRequest();

Sending a request object (contd.)• HTTP_Request is an object class which extends a base

class called the PEAR base class• The PEAR base class contains a range of methods -- see

Chapter 26 of the PEAR manual, which is available at http://pear.php.net/manual/index.php

• One of these is the isError method which checks for a PEAR_Error object

• Format of callboolean PEAR::isError (mixed $data [, mixed $msgcode])

• It can be used to see whether an error is produced when a HTTP request is sent

• Example 2$request =& new HTTP_Request("http://www.rte.ie/");

if ( ! PEAR::isError( $request->sendRequest()) )

{ ......... }

Revisiting the example client program in PHP

<?php




{


echo $contents;

}

?>• Note we have not handled fact that

some URLs on RTE site are relative• Thus, output not quite right -- some

image URLs are not quite right

Revisiting, again, the example client program

<?php




{


$contents=

str_replace('src="/',

'src="http://www.rte.ie/',

$contents);

echo $contents;

}

?>• We have handled some of the relative

URLs on RTE site• But, output still not quite right

Revisiting, yet again, the example client program

<?php




{


$contents=

str_replace('src="/',


$contents);

$regexp = '%src="(?!http://)%';

$contents=

preg_replace($regexp,


$contents);

echo $contents;

}

?>

• A utility which shows all data from incoming requests is here: http://www.cs.ucc.ie/j.bowen/cs4408/resources/showRequest.php

• It is defined as follows:

<?php

echo "SERVER variables: ";

foreach ($_SERVER as $name => $value)

{ echo "$name = $value "; }

echo "GET variables: ";

foreach ($_GET as $name => $value)


echo "POST variables: ";

foreach ($_POST as $name => $value)


echo "COOKIE variables: ";

foreach ($_COOKIE as $name => $value)


?>

When called by a MSIE browser

Consider this "browser" calling the same showRequest.php

• It is a PHP program at http://cosmos.ucc.ie/~jabowen/cs4408/myBrowser.php

• It is implemented as follows:<?php

require_once "HTTP/Request.php";$req = & new

HTTP_Request("http://www.cs.ucc.ie/j.bowen/cs4408/resources/showRequest.php");


{ $contents= $req->getResponseBody();

echo $contents;

}

?>

Output from showRequest.php when called by "browser"

Sending headers

A modified "browser"

• It is a PHP program at http://cosmos.ucc.ie/~jabowen/cs4408/myBrowser2.php


require_once "HTTP/Request.php";$req = & new

HTTP_Request("http://www.cs.ucc.ie/j.bowen/cs4408/resources/showRequest.php");

$req->addHeader('ACCEPT-LANGUAGE','en-ie'); if (!PEAR::isError($req->sendRequest()))


echo $contents;

}

?>

Output from showRequest.php when called by "browser"ACCEPT_LANGUAGE header now appears

Handling cookies

• Modified utility to show all data from incoming requests: http://www.cs.ucc.ie/j.bowen/cs4408/resources/showRequest2.php

<?php

ob_start();

setcookie('dummyCookie','baconAndEggs');

ob_end_flush();echo "SERVER variables: ";

foreach ($_SERVER as $name => $value)


echo "GET variables: ";

foreach ($_GET as $name => $value)


echo "POST variables: ";

foreach ($_POST as $name => $value)


echo "COOKIE variables: ";

foreach ($_COOKIE as $name => $value)


?>

In first call by a MSIE browser, no cookie comes in request

In second call by a MSIE browser, a cookie is in request

A "browser" to read showRequest2.php

• It is a PHP program at http://cosmos.ucc.ie/~jabowen/cs4408/myBrowser3.php


require_once "HTTP/Request.php";$req = & new HTTP_Request("http://www.cs.ucc.ie/j.bowen/cs4408/resources/showRequest2.php");

$req->addHeader('ACCEPT-LANGUAGE','en-ie'); if (!PEAR::isError($req->sendRequest()))


echo $contents;

}

?>

cs 4408 got here on 4 nov 2005

In first call, no cookie comes in request

No cookie comes in 2nd call either

Why no cookie in 2nd request?

• We know that showRequest2.php sent a cookie to our "browser" when it sent a response to the first request

• Why did that cookie not come back in the 2nd request?

• Because our "browser" does not maintain a "cookie jar" and never sends cookies

Cookie "jars"

• A cookie "jar" is the mechanism used by a HTTP client to store cookies it receives from servers

In MSIE, the cookie jar is a directory on the hard-disk of the client machine; each cookie is file

In Netscape 8.0, the cookie jar appears to be a single file managed by an interface which allows you to see cookie properties

In Firefox, the cookie jar appears to be a single file managed by an interface which allows you to see cookie properties

Detecting cookies

• Before we implement a cookie jar in our web client, let's first make our "browser" report cookies that it receives from the server-side program

A "browser" to read showRequest2.php and which can show cookies and other headers that are sent by the server

• At http://cosmos.ucc.ie/~jabowen/cs4408/myBrowser4.php

<?phprequire_once "HTTP/Request.php";

$req = & new HTTP_Request("http://www.cs.ucc.ie/j.bowen/cs4408/resources/showRequest2.php");


{ $headers = $req->getResponseHeader();

echo " Headers";

foreach ($headers as $name => $value)

{ echo " $name = $value"; }

echo " Cookies ";

$cookies = $req->getResponseCookies();

foreach ($cookies as $fields)

{ foreach ($fields as $name => $value) { echo "$name = $value; "; } echo " "; }


echo " Body ";

echo $contents;

}

?>

Adding a cookie jar to our web client

• We could use a simple text file as our cookie jar

• Initially, let's have a simple jar, which stores only the names and values of cookies, without storing such attributes a expiry date, web-address, etc

• Let's call the file cookieJar

A "browser" to read showRequest2.php and which remembers and returns a cookie sent by the server

• At http://cosmos.ucc.ie/~jabowen/cs4408/myBrowser5.php<?php


$req = &

new HTTP_Request("http://www.cs.ucc.ie/j.bowen/cs4408/resources/showRequest2.php");

$fp=fopen("tmp/cookieJar","r"); $cookie = fread($fp,100); fclose($fp);

if ($cookie) { $pieces=explode("=",$cookie); $req->addCookie($pieces[0],$pieces[1]); }


{ echo " Non-cookie Headers received by Browser";

$headers = $req->getResponseHeader();

foreach ($headers as $name => $value) { echo " $name = $value"; }

echo " Cookies received by browser ";

$cookies = $req->getResponseCookies();

$fp=fopen("tmp/cookieJar","w");

foreach ($cookies as $fields)

{ foreach ($fields as $name => $value ) { echo "$name = $value; "; }

echo " "; fwrite($fp,"$name=$value"); }

fclose($fp);


echo " Message Body rec'd by Browser "; echo $contents;

}

?>

Before 1st call, cookieJar is empty; so, no cookie is sent

However, after the request the cookieJar is not empty, as we can see in the vi session below

Since cookieJar is no longer empty, a cookie is sent the next time we run our "browser"; its arrival is reported by server-side program

Building HTTP clients in PHP. A PHP package for sending HTTP requests and getting responses A PHP...

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