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Professional Information Technology-Programming Book part 77

Không đóng trình duyệt đến khi xuất hiện nút TẢI XUỐNG Tải xuống

Tham khảo tài liệu 'professional information technology-programming book part 77', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Cookies Cookies are small pieces of information that are stored in your web browser. They typically contain data that is used to identify you when you look at a website so that site can be customized for each visitor. Rather than having to pass data to a script by using a form or as values in the query string cookies are sent back to your scripts automatically by your web browser. Even if you go off and browse to another website their values are remembered when you return. For example if you have to log in to access a particular website you may be able to let a cookie remember your username so you do not have to type it each time you go back in this case you only have to enter your password. Or on a community site your browser might record the date you last visited in a cookie so that any forum messages posted since you last visited can be highlighted as new. Cookie Ingredients Each cookie consists of a name and a value just like regular variables in PHP. The instruction to create a cookie in your web browser is sent as an HTTP header before a web page is transmitted when your web browser sees this header it takes the appropriate action. The HTTP headers that create cookies are the same regardless of whether they are generated by PHP or any other means of interfacing with your web server. The header used to set a cookie called email might look like this Set-Cookie email chris@lightwood.net HTTP Headers You will never see an actual HTTP header in your web browser. We will look at how different types of HTTP headers are sent in PHP in Lesson 16 Communicating with the Web Server. A cookie also has an expiration date some cookies last only as long as your web browser is open and are kept in your computer s memory whereas others have a fixed expiration date in the future and are saved to your hard disk. The HTTP header to set the email cookie that will expire at the end of 2005 would look like this Set-Cookie email chris@lightwood.net expires Sat 31-Dec-2005 23 59 59 .