2. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 1 Lecture 4: Server-side Languages Instructor: Dr. Mohammad Anwar Hossain

3. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 2 Learning Outcomes In this chapter, you will learn about: ◦ The market for server-side Web development solutions is a crowded one, these days! Perl, ASP, PHP, JSP, Cold Fusion and many more specialized choices abound. ◦ The choice of a server-side programming language is a constant source of heated debate on the Internet today. ◦ For making advanced dynamic web sites, you need some kind of server side scripting. Server side scripts are programs that are executed on the server, and can be used in many clients.

4. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 3 Review Had a look at basic protocols – HTTP Looked at static web pages – HTML Experimented with dynamic client-side scripting - JavaScript Studied methods of capturing and transforming data - XML

5. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 4 Today Overview of the Server-side Client-server architecture Static to dynamic - why we need it Development history Server-side languages now available Servers

6. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 5 Web Pages Layers Web pages have 3 layers… Structural/Content Layer (XHTML) ◦ The meat and potatoes Presentational Layer (CSS) ◦ How things look; garnishing the meat and potatoes on a pretty plate Behavioral Layer (JavaScript and DOM) ◦ How websites behave; the meat can jump off the plate if you want it to.

7. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 6 Client-side Languages User-agent (web browser) requests a web page http request http response Web page (with JavaScript) is sent to PC JavaScript is executed on PC Can affect the Browser and the page itself

8. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 7 Client-side What kind of things can you do with JavaScript? Validating Form information, ◦ i.e., making sure all the fields are complete before submitting data back to the server Modifying a web page based on Mouse Events. ◦ Can turn a web page into a user interface with interactive buttons and controls

9. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 8 Server-side Languages User-agent (web browser) requests a web page http request Server detects PHP code in page, executes the code, and sends the output to the user http response Web page (with PHP Output) sent to PC User never sees the PHP, only the output Cannot affect the browser or client PC

10. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 9 Internet Laptop Apple Mac PC Web Server HTTP ClientsHTTP Server HTTP Over Internet (TCP/IP) HTTP Protocol

11. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 10 Server-side Programming Skills that are often required: CGI PHP ASP Perl Java Servlet, … Web Client Web Server Internet Client-side Programming Skills that are often required: XHTML Javascript Java Dreamweaver Flash SMIL, XML … Database Server side and Client side Programming

12. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 11 ServerBrowser Request Reply File System Static Web Model

13. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 12 ServerBrowser Request Reply File System Dynamic Web Model - Server-Side Includes (SSI), Active Server Pages (ASP), Java Server Pages (JSP), PHP Hypertext Processor (PHP), Perl … Other Programs

14. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 13 Static to dynamic, a case study

15. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 14 Static to dynamic, a case study This is the story of a fictional news site and how it evolved over time.

16. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 15 Version 1.0 (Static only) HTML and images only Large collection of news articles Good navigation in header and in footer

17. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 16 Version 1.1 (Dynamic, using SSI) Navigation headers and footers have to change on every page Converted to using Server-Side Includes (SSI) to avoid having to update every file the next time this happens.

18. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 17 SSI defined Server Side Includes (SSI) are HTML comment tags which contain commands directed at the Web server. The server carries out these commands not the browser. Not all servers react to SSI commands the same.

19. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 18 How SSI works When the server parses a document it searches through the page, looking for special commands that it recognizes. When it finds a command like “input today’s date, or insert this code snippet, it acts on the command and rewrites your web page for you.

20. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 19 How SSI works If you want your document to be parsed, you need to name the file with an extension of.shtml. When the server loads any document that ends with.shtml, it knows that is has to check for hidden SSI commands first.

21. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 20 Server-Side Includes (SSI) Web server reads the file as it sends it out to the user’s web browser Looks for SSI instructions in the file and executes them, replacing the instruction with the output from the command Allows for simple header and footer includes but no programming logic

22. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 21 Example of SSI Example of SSI The layout of this page is fully controlled by a common file. There are no BODY, COLOR or TABLE tags in this page. where layout_top.html has side bar and layout_bottom.html has Server Side Include (SSI) Example

23. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 22 Version 1.2 (Dynamic, with CGI) HTML form with user submissions CGI program to process submissions, send them to the editors of the site. –Retrieve data from CGI environment –Send mail to editors –Send redirect to user's web browser

24. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 23 Common Gateway Interface (CGI) CGI stands for Common Gateway Interface CGI is a standard programming interface to Web servers that allows building dynamic and interactive Web sites CGI is not a programming language. ◦ It is just a set of standards (protocols) ◦ The standards specify how Web-applications can be executed on the server-side

25. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 24 Common Gateway Interface (CGI) CGI can be implemented ◦ in an interpreted language such as PERL ◦ in a compiled language such as C Any program can be converted to a CGI program ◦ It just has to follow the CGI rules The rules define ◦ How programs get and sends data (i.e., communication protocol) ◦ How to make sure Web server knows that a program is a CGI program.

26. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 25 CGI A CGI program is ◦ Stored on the server, ◦ Executed on the server, ◦ Executed in response to request from client. By running a CGI program, rather than delivering a static HTML page, the server can: ◦ Put dynamic and updated information on web page (e.g., weather forecast, stocks price, product availability, etc…). ◦ Respond appropriately to user input. ◦ Store user data on server-side in a file or DB.

27. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 26 Dynamic Pages Run CGI program … print $result Return dynamically generated HTML file Request service <BODY

28. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 27 Version 1.3 (User login, sessions) Optional user login ability added to site Session management required Some pages in web site have to detect if the user is logged in and behave differently Server-side scripting used, session management abilities built in

29. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 28 HTTP State and Session What is a session? ◦ A serial of consecutive and related requests from and responses to a single client, in a certain duration and scope What is state? ◦ State is the information to describe or identify a session at a certain point of time ◦ Stateful: each request/response can maintain its state at different points of times  Phone calls are stateful ◦ Stateless: each request/response cannot maintain its state at different points of times  HTTP protocol is stateless, i.e., HTTP itself does not provide mechanisms to maintain state information for each request/response. In other words, HTTP does not remember.

30. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 29 Applications Where is session/state needed? ◦ User sign-in status ◦ A transaction involving multiple steps (requests/responses), such as  shopping (cart)  multi-page survey or multi-page test  auto insurance quote ◦ User preferences, personalization, customization ◦ …

31. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 30 Version 2.0 Version 1.3 used 3 different technologies. (SSI, CGI program, server-side scripting) Everything can be done by one technology, server-side scripting. Converting the SSI pages (every page) to server-side scripting increases flexibility for additional features. PHP

32. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 31 Why use server-side scripting? Written for the Web Libraries, APIs, interfaces for Web applications Web page output is the focus, code is the exception Easy to pick up and start using immediately As fast or faster than CGI programs and more secure.

33. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 32 Which server-side language is best? Simply a question of what is best for your environment and what you need to be able to do with the language Comparative speed is irrelevant –Design of application the largest factor –Database or storage system speed next biggest factor

34. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 33 Picking a language: Criteria Availability –A stable platform (server) to run it on –People who can write and maintain programs using it Interoperability with other applications Security –Security reputation of the language, especially with respect to applications or servers dealing with sensitive data

35. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 34 CGI servicing programs ISAPI servicing programs (Internet Server API, programs which integrate with web server and therefore faster) JavaScript VBScript Server-side Includes (SSI) Common Gateway Interface (CGI) Active Server Pages (ASPs) PHP Java Server Pages (JSPs) Perl Web / Database Technologies Client-side Processing Server-side Processing Compiled Programs Server-side Scripts Client-side Scripts Downloading and running compiled programs on client Applets ActiveX Choices Server/Client Sides - overview

36. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 35 ServerBrowser Request Reply File System Dynamic Web Model – Common Gateway Interface (CGI) (Security Problems?) CGI Program Other Programs

37. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 36 PHP Strengths High performance - see benchmarks at http://www.zend.com http://www.zend.com Interfaces to different database systems Low cost Various packages include Apache, PHP and MySQL for many OS Ease of learning and use Portability

38. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 37 PHP 4 Architecture Language parser = self-contained component called The Zend Engine. PHP function modules, now called PHP extensions, are also basically self-contained. Web server abstraction layer called SAPI that greatly simplifies the task of adding native support for new Web servers. PHP 4's architecture: Top border of the figure represents the programmer's interface (meaning all except for the Web server):

39. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 38 Server Choice - Web Servers Use such protocols as HTTP (HyperText Transfer Protocol), FTP (File Transfer Protocol) and SMTP (Simple Mail Transfer Protocol) The Web Server, using HTTP, accepts HTTP requests from Web Browsers (Internet Explorer, Netscape, Opera etc.) and returns the requested HTML pages, images, embedded Java applets etc This can be enhanced by a number of server-side (running on the Web Server) technologies. These include CGI scripts, server-side includes, SSL security, Java servlets, ASP etc.

40. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 39 Web Servers Although a Web Server may be considered a network server, it has unique web networking features: –Handles permissions –Executes programs –Keeps track of directories and files –Communicates with client computers A server may be a powerful PC, a minicomputer or even a mainframe. Many Web Servers run on the UNIX operating system (60%), although a fair number use Microsoft’s NT OS (40%) – ZD Net Tech InfoBase

41. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 40 Apache Web Server The leading UNIX web server (therefore most common to be found on the Internet) It is a high performance HTTPD (HTTP daemon) server – A daemon is a background process in UNIX which implements the server-side of a protocol HTTPD is the program you would run on a UNIX platform to start the web server Apache Web Server - developed by the Apache Group. UNIX and Windows). Tools, languages and modules available; SSL (port 443) Versions 1.3 and 2.0 http://www.apache.org

42. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 41 Microsoft IIS IIS = Internet Information Server Extends Windows NT Server to Intranet and Internet Works closely with NT Services, Security and Monitoring Adds – WWW Service, Gopher, FTP, Internet Service Manager (admin tools), Internet Database Connector (IDC), Secure Socket Layer (SSL) IIS 2.0 is part of NT 4.0, IIS 5 is part of Windows 2000 http://www.microsoft.com/ntserver/Basics/WebServices/ Provides full Intranet and Internet capabilities, from publishing information to access to data stored in databases Supports CGI (Common Gateway Interface) – although with poor memory management

43. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 42 Summary Architectures and protocols Static serving to dynamic Case history of an application Server-side languages reviewed Which server? http://www.w3.org/Servers.html

44. Modified from Moseley ’s sli desWeb Applications Development. Lecture 4 Slide 43 Next Introduction to PHP