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Publishing AJAX and PHP - part 2

Mặc dù lịch sử của Internet là một chút nữa, 1991 là năm khi HyperText Transfer Protocol (HTTP), mà vẫn được sử dụng để truyền dữ liệu qua Internet, được phát minh. Trong phiên bản đầu tiên của nó ban đầu, nó đã không làm nhiều hơn việc mở và đóng kết nối. Các phiên bản sau này của HTTP (phiên bản 1.0 xuất hiện vào năm 1996 và phiên bản 1.1 năm 1999) đã trở thành giao thức mà bây giờ chúng ta đều biết và sử dụng | AJAX and the Future of Web Applications Building Websites Since 1990 Although the history of the Internet is a bit longer 1991 is the year when HyperText Transfer Protocol HTTP which is still used to transfer data over the Internet was invented. In its first few initial versions it didn t do much more than opening and closing connections. The later versions of HTTP version 1.0 appeared in 1996 and version 1.1 in 1999 became the protocol that now we all know and use. HTTP and HTML HTTP is supported by all web browsers and it does very well the job it was conceived for retrieving simple web content. Whenever you request a web page using your favorite web browser the HTTP protocol is assumed. So for example when you type www.mozilla.org in the location bar of Firefox it will assume by default that you meant http www.mozilla.org. The standard document type of the Internet is HyperText Markup Language HTML and it is built of markup that web browsers understand parse and display. HTML is a language that describes documents formatting and content which is basically composed of static text and images. HTML wasn t designed for building complex web applications with interactive content or user-friendly interfaces. When you need to get to another HTML page via HTTP you need to initiate a full page reload and the HTML page you requested must exist at the mentioned location as a static document prior to the request. It s obvious that these restrictions don t really encourage building anything interesting. Nevertheless HTTP and HTML are still a very successful pair that both web servers and web clients browsers understand. They are the foundation of the Internet as we know it today. Figure 1.1 shows a simple transaction when a user requests a web page from the Internet using the HTTP protocol web server replies by sending back the contents of index.html client requests ndex.html via HTTP Figure 1.1 A Simple HTTP Request 10 Chapter 1 Three points for you to keep in mind 1. HTTP .