Detailed explanation of php cookie working principle and examples

This article mainly introduces how to use PHP cookies. PHP cookies are often used in the PHP development process. Code examples are given here for easy understanding. Friends in need can take a look at

Cookies in php are commonly used by us, but many friends may not know how cookies work. The editor below will sort out the working principles of php cookies

and some examples of cookie reading and writing operations.

Cookie and Session State

These two concepts are essential for BS development. Let’s have a general understanding first. It is difficult to go into depth without practical application. Please read the reference in depth. address!
What is Cookie?

A cookie is a small piece of text information that is passed between a web server and a browser along with user requests and pages. The information contained in the cookie can be read by the web application each time the user visits the site. Basics of How Cookies Work If a user returns to a page on the site and enters the URL www.*****.com, the browser looks for a cookie associated with that URL on the local hard drive. If the cookie exists, the browser sends it to your site with the page request.

What are the uses of cookies?

The most fundamental purpose is: Cookies can help Web sites save information about visitors. More generally, cookies are a way to maintain the continuity of Web applications (that is, to perform "state management") and to enable the Web site to remember you.

•When a customer visits a website based on PHP technology At this time, you can use the setcookie() function in PHP to generate a cookie. After processing, the system sends the cookie to the client and saves it in the C:Documents andSettings username Cookies directory.

•Cookies are part of the HTTP header, so the setcookie() function must be called before any content of the HTML itself is sent to the browser. This restriction is the same as the header() function (if you need to understand the head() function, please check it yourself).

•When the customer visits the website again, the browser will automatically send the cookie corresponding to the website in the C:DocumentsandSettings username Cookies directory to the server, and the server will automatically send the cookie sent from the client. into a PHP variable. In PHP5, cookies sent by the client will be converted into global variables. You can read it through $_COOKIE['xxx'].

Define a cookie

•Set cookie:

•Syntax: boolsetcookie(stringname,[stringvalue,[int expire,[stringpath ,[stringdomain,[int secure]]]]]);

This cookie function can have 6 attributes, and the commonly used ones have 3 parameters.

1. Example:

The code is as follows

$value="the best way is by yourself";
setcookie("cookiename",$value,time()+60*60*24*7);

1. Receive and process cookies

PHP has good support for cookies Supported, just like the form form, PHP will automatically receive the HTTP header from the web server and process it when receiving. When receiving, use $_COOKIE["cookiename"] or $HTTP_COOKIE_VARS["cookiename"] (not recommended)

1. Note:

If the website has several different file directories and uses a cookie without a path, the cookie can only be accessed in the path of the file where the cookie is set. If a path is specified, the path when setting will be used as the specified path to access the cookie.

Create cookie array:

1. The first one:

The code is as follows

setcookie("CookieArray[0]","Value1");
setcookie("CookieArray[1]","Value2");

1. The second one:

The code is as follows

setcookie("CookieArray['one']","Value1");
setcookie("CookieArray['two']","Value2");

1. Use array in setcookie()

The code is as follows

<?php
setcookie("cookie[three]","cookiethree");
setcookie("cookie[two]","cookietwo");
setcookie("cookie[one]","cookieone");
//刷新页面后，显示出来
if(isset($_COOKIE[&#39;cookie&#39;])){
foreach($_COOKIE[&#39;cookie&#39;]as$name=>$value){
echo"$name:$value<br/>n";
}
}
?>

Delete cookie

1 .To delete an existing cookie, there are two ways:

1. Call setcookie with only the name parameter, then the cookie with this name will be deleted from the client;
setcookie ("MyCookie");//Delete MyCookie

2, the period is enough, then the cookie will be deleted (actually invalid) after browsing this page.

For example:

The code is as follows

setcookie(“MyCookie”,”Value”,time()-1);

//Delete MyCookie.

Note: When a cookie is deleted, its value is still valid on the current page. If you want to set the cookie to expire after the browser is closed. Then you can directly set expiretime to 0, or do not set this value.

For example: setcookie("name","value",0).

Cookie Notes

•1. There cannot be any html output before setcookie(), even spaces and blank lines will not work. It must be before the content of the html file is output. Setting

•2. After setcookie(), there will be no output when you call echo$_COOKIE["name"] on the current page. You must refresh or go to the next page to see the cookie value.

•3. There is no need for browsers to handle cookies differently. The client can disable cookies, and the browser will also limit the number of cookies. The maximum number of cookies that can be created by a browser is 300, and each cookie cannot exceed 4KB. The total number of cookies that can be set by each WEB site cannot exceed 20.

•4. Cookies are stored on the client side. If the user disables cookies, your cookies will naturally have no effect! Therefore, avoid over-reliance on cookies and think about solutions if cookies are disabled, just in case.

Summary: The above is the entire content of this article, I hope it will be helpful to everyone's study.

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