2.2 Web Server

A web server is the combination of computer and the program installed on it. Web server interacts with the client through a web browser. It delivers the web pages to the client and to an application by using the web browser and  he HTTP protocols respectively. We can also define the web server as the package of  large number of programs installed on a computer connected to Internet or intranet for downloading the requested files using File Transfer Protocol, serving e-mail and building and publishing web pages. A web server works on a client server model. A computer connected to the Internet or intranet must have a server program. While talking about Java language then a web server is a server that is used to support the web component like the Servlet and JSP. Note that the web server does not support to EJB (business logic component) component. A computer connected to the Internet for providing the services to a small  company or a departmental store may contain the HTTP server (to access and store the web pages and files), SMTP server (to support mail services), FTP server ( for files downloading) and NNTP server (for newsgroup). The computer containing all the above servers is called the web server. Internet service providers and large companies may have all the servers like HTTP server, SMTP server, FTP server and many more on separate machines. In case of Java, a web server can be defined as the server that only supports to the web component like servlet and jsp. Notice that it does not support to the business component like EJB.

2.3 Php and json

PHP is the most popular scripting language on the web. It is used to enhance web pages. With PHP, programmers can do things like create username and password login pages, check details from a form, create forums, picture galleries, surveys, and a whole lot more. If you've come across a web page that ends in PHP, then the author has written some programming code to liven up the plain, old HTML. PHP is known as a server-sided language. That's because the PHP doesn't get executed on your computer, but on the computer you requested the page from. The results are then handed over to you, and displayed in your browser. Other scripting languages you may have heard of are ASP, Python and Perl. The most popular explanation of just what PHP stands for is "Hypertext Pre-processor". An alternative explanation is that the initials come from the earliest version of the program, which was called Personal Home Page Tools.

JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the JavaScript programming language. JSON is a text format that is completely language independent but uses conventions that are familiar to programmers of the C-family of languages, including C, C++, C#, Java, JavaScript, Perl, Python, and many others. These properties make JSON an ideal data-interchange language. JSON is built on two structures: A collection of name/value pairs. In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array. An ordered list of values. In most languages, this is realized as an array, vector, list, or sequence. These are universal data structures. Virtually all modern programming languages support them in one form or another. It makes sense that a data format that is interchangeable with programming languages also be based on these structures.