{"id":21,"date":"2018-07-12T06:17:17","date_gmt":"2018-07-12T06:17:17","guid":{"rendered":"http:\/\/itp9.epgpbooks.inflibnet.ac.in\/?post_type=chapter&p=21"},"modified":"2024-01-19T07:20:13","modified_gmt":"2024-01-19T07:20:13","slug":"introduction-to-web-development-with-php","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/itp9\/chapter\/introduction-to-web-development-with-php\/","title":{"rendered":"Introduction to Web Development with PHP"},"content":{"raw":"
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The World Wide Web or simply Web consists of many components. These components work together to display web page. Web Applications use client\/server architecture. This architecture has mainly 3 components.<\/p>\r\n1. Client\r\n\r\n2. Network\r\n\r\n3. Server\r\n\r\n \r\n

Client connects to the server by Internet. Client send request to the server and server response to the client. Server shares resources with clients. These resources can be files, printers, web sites, databases, emails. The server which share web site is known as Web server. In the same way, if a server share files, it is called file server. Client software is used web browser software to access web server. Client and server are communicated by a communication system. This communication system is known as network.<\/p>\r\n \r\n

Computer connects to the network through NIC (Network Interface Card). The connection between client and server through network can be wired or wireless. Ethernet is a common type of wired network. The most common type of wireless network is Wi-Fi.<\/p>\r\n \r\n\r\nThe information is transported from one computer to another by network.\r\n\r\n \r\n

Routing is the process to determine route to get information from one computer to another. A router is a device that is connected to two or more networks. Router determines the route to communicate between source and destination. When information comes from source network, router decides which network is closets to the destination network and sends information to the closets network.<\/p>\r\n \r\n\r\nNetwork can be categorized by size. According to the size network can be classified as LAN, MAN and WAN.\r\n\r\n \r\n

LAN (Local Area Network) is a small network of computers. The computers are communicating for short distance in LAN. LAN is used to connect computers in the same building or in adjacent buildings. This type of network is used as intranet. Intranet can be used to run web applications for use by employees only.<\/p>\r\n \r\n

A Wide Area Network (WAN) consists of multiple LANs. Many LANs can be connected one WAN. WANs are connected together over long distance using routers. A WAN can be proprietary to one company or it can be shared by multiple companies. WAN is owned by an Internet Service Provider (ISP). ISP owns WAN which are connected to the Internet. Any company want to use Internet can lease access from ISP.<\/p>\r\n \r\n

The Internet is network of network. Internet consists of multiple WANs. All these WANs have connected together. ISPs connect their WANs together by Internet Exchange Points (IXP). IXPs is considers as large routers. This architecture allows anyone connected to the Internet to exchange information with anyone else.<\/p>\r\n \r\n\r\nThe following diagram shows how data are travelled in Internet.\r\n\r\n<\/div>\r\n\"\"\r\n

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In the diagram. Client sends data to the server.\u00a0 Data travel from LAN to WAN to the IXP. The WAN is owned by client\u2019s ISP. WAN is owned by ISP. There may be different ISP for client and server. The time taken to complete the request\/response on Internet is less than 1\/10th of a second.<\/p>\r\n \r\n

Web Pages are mainly classified as static web page and dynamic web pages.<\/p>\r\n \r\n

A static web page is a web page which only changed when web developer change it. It does not give you output according to your query. It is a plain text file. It contains all the content to be displayed in the web browser.<\/p>\r\n \r\n

Following figure shows how a web server processes static web page.<\/p>\r\n\"\"\r\n\r\n \r\n

User asks web page by typing URL (Uniform Resource Locator) into the address bar of web browser or click on a link from current page. Now the web browser sends a request for the web page to the web server. The protocol used for request a web page is HTTP (Hyper Text Transfer Protocol). So this is known as HTTP request. When the web server receives HTTP request, the web server searches for requested web page in disk drive. The retrieved web page send to the browser. The response of HTTP request, provided by web server is known as HTTP response. Browser understand only HTML. Hence, the result web page is rendered as HTML in web browser.<\/p>\r\n\r\n<\/div>\r\n

\r\n\r\n \r\n\r\nTCP\/IP\u00a0 (Transmission\u00a0 Control\u00a0 Protocol\/Internet\u00a0 Protocol)\u00a0 is\u00a0 a\u00a0 suite\u00a0 of\u00a0 protocol.\r\n\r\n \r\n\r\nTCP\/IP allows two computers to communicate over a Network.\r\n\r\n \r\n

A dynamic web page is a web page which changed as per the query. Dynamic web page shows output according to query. Dynamic web page is created by program or script. The program or script resides on the web server.<\/p>\r\n \r\n\r\nFollowing figure shows how a web server processes dynamic web page.\r\n\r\n\"\"\r\n\r\n \r\n

User asks web page by typing URL (Uniform Resource Locator) into the address bar of web browser or click on a link from current page. Now the web browser sends a request for the web page to the web server. The protocol used for request a web page is HTTP (Hyper Text Transfer Protocol). So this is known as HTTP request. When the web server receives HTTP request, the web server determines the file extension. File extension is determined by application mapping program of web server. Once file extension is determined, then the application engine process the request. For example, if the file extension is .php, then the web server forward the HTTP request to PHP interpreter. The PHP interpreter running on the web server. PHP interpreter processes the request. During the processing, if any data require then PHP application engine communicate with database server for data. Once the processing has completed, PHP interpreter pass the dynamically generated web page to the web server. Web server send page back to the browser as HTTP response. HTTP response includes HTML. On receiving HTTP response, the web browser format and display web page.<\/p>\r\n \r\n

Formatting and displaying HTTP response in browser is known as rendering the web page. Rendering is happen for static or dynamic web page.<\/p>\r\n \r\n\r\nOnce the page is display in browser, the user can view the content.\r\n\r\n \r\n\r\nWhen the user request another page, the same process is begin again.\r\n\r\n \r\n

The process that starts when client requesting a web page and ends with server sending response of the request to the client is known as round trip.<\/p>\r\n \r\n

Now let us look at the most common software for web application development.<\/span><\/p>\r\n \r\n

The most common used web browsers are Internet Explorer, Firefox, Chrome, Safari and Opera. Internet Explorer is Microsoft Proprietary. Firefox is published by Mozila. Safari is Apple product. Chrome is Google proprietary. Opera is published by Opera. Most of the browser can supports for major operating systems like Microsoft, Linux, Apple.<\/span><\/p>\r\n \r\n

The most common web servers used nowadays are Apache and IIS. Apache is an open source web server. Apache can run on major operating systems. Apache can support many database servers also. The most common configuration in web development is LAMP, which is acronym for Linux (Operating System), Apache (Web Server), MySQL (Database Server) and PHP (Web Application Engine). IIS is Microsoft proprietary product. IIS runs only on windows operating system. IIS mainly used for ASP.NET Web Applications and SQL Server database. IIS is a short form of Internet Information Services.<\/span><\/p>\r\n \r\n

The most common server side scripting languages are PHP, JSP, ASP.NET, Perl and Python. PHP is open source web engine mainly used with Apache Web server. JSP also works with Apache. JSP generally work with servlets. The servlets are written in Java. ASP.NET is used with IIS. ASP.NET is used VB or C# for server side scripting. Perl is originally developed to work with Unix. Python is used for many types of application now a days.<\/span><\/p>\r\n \r\n

The most usable database servers are MySQL, Oracle, DB2 and SQL Server. MySQL is initially an open source database. MySQL is now acquired by Oracle. Oracle database is Oracle\u2019s proprietary database server which can run on major operating systems. DB2 is a product from IBM that is also available for major operating system. MS SQL Server can run only on Microsoft operating system.<\/span><\/p>\r\n\r\n<\/div>\r\n

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HTML<\/strong><\/p>\r\n \r\n

HTML stands for Hyper Text Markup Language. Only HTML pages make static web application. HTML is invented by Tim Berners-Lee. HTML is derived from SGML (standard General Markup Language). HTML has predefined tags. Tags are defined by opening and closing angle brackets(< >). There are opening and closing tags. The content is written between opening and closing tag. The closing is preceded by slash (<\/>). Tags are generally written in lowercase. Some tags do not require closing tags while some tags required opening and closing tag. A tag can have attributes. Attribute has value. A tag can have more than one attribute. Attribute should write inside double quotes (\u201c \u201c). Though to write attribute in double quotes is not compulsory for HTML, but it makes HTML page, XHTML compatible also.<\/p>\r\n \r\n

XHTML is short form of eXtensible Hyper Text Markup Language. XHTML is very similar to HTML 4.01. XHTML syntaxes are more strict then HTML. XHTML makes HTML compatible to XML. XHTML is supported by many leading browsers.<\/p>\r\n \r\n\r\nThere are very few differences between HTML and XHTML.\r\n\r\n<\/div>\r\n

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