Detailed explanation of php cookie operations (setting, use, deletion)

1. Set Cookie To set cookies in php, use the SetCookie function. Note: Cookie is part of the HTTP protocol header and is used to transfer information between the browser and the server, so the Cookie function must be called before any content belonging to the HTML file itself is output.

The SetCookie function defines a Cookie and appends it to the end of the HTTP header. The prototype of the SetCookie function is as follows:

All parameters except name are optional. The three parameters value, path, and domain can be replaced with empty strings, indicating that they are not set; the expire and secure parameters are numerical and can be represented by 0. The expire parameter is a standard Unix time stamp, which can be obtained using the time() or mktime() function, in seconds. The secure parameter indicates whether this cookie is transmitted over the network through the encrypted HTTPS protocol.

The currently set cookie does not take effect immediately, but will not be visible until the next page. This is because the cookie is passed from the server to the client's browser on the set page, and the browser can transfer the cookie from the client to the next page. The reason why the file is retrieved from the machine and returned to the server. Setting cookies on the same page actually starts from back to front, so if you want to delete a new cookie before inserting it, you must first write the insertion statement and then the delete statement, otherwise undesirable results may occur. .

Let’s look at a few examples of the SetCookie() function setting cookies.

--Simple: SetCookie("MyCookie", "Value of MyCookie");

--with expiration time: SetCookie("WithExpire", "Expire in 1 hour", time()+3600);//3600 seconds=1 hour

--Comprehensive type: SetCookie("FullCookie", "Full cookie value", time()+3600, "/forum", ".jbxue.com", 1);

If the site has several different directories and only uses cookies without paths, the cookies set in the pages in one directory will not be visible in the pages in another directory. Cookies are path-oriented. Even if the path is not specified, the WEB server will automatically pass the current path to the browser, and specifying the path will force the server to use the set path. Solution: Add the path and domain name when calling SetCookie. The format of the domain name can be "bbs.it-home.org" or ".jbxue.com".

The part representing the value in the SetCookie function will be automatically encoded when passed. If the value of value is "test value", it becomes "test%20value" when passed, the same as the method of URL. This is transparent to the program, and PHP will automatically decode the cookie value when it receives it.

To set multiple cookies with the same name, use an array:

2. Receive and process Cookies

PHP has very good support for receiving and processing cookies. It is completely automatic and has the same principle as FORM variables. It is very simple. For example, if you set a cookie named MyCookier, PHP will automatically analyze it from the HTTP header received by the WEB server and form a variable like an ordinary variable named $myCookie. The value of this variable is the value of the cookie. The same applies to arrays.

Another way is to reference PHP’s global variable $HTTP_COOKIE_VARS array.

The examples are as follows: (assuming these have been set in previous pages and are still valid)

It’s that simple.

3. Delete Cookies To delete an existing cookie, there are two ways: One is to call SetCookie with only the name parameter, then the cookie named this name will be deleted from the related client computer; Another way is to set the cookie expiration time to time() or time()-1, then the cookie will be deleted (actually expired) after the page is browsed. Note: When a cookie is deleted, its value is still valid on the current page.

4. Restrictions on using cookies First, it must be set before the content of the HTML file is output;

Secondly, different browsers handle cookies inconsistently, and sometimes incorrect results may occur. For example: MS IE+SERVICE PACK 1 cannot correctly handle Cookies with domain name and path, Netscape Communicator 4.05 and MS IE 3.0 cannot correctly handle Cookies without path and time. As for MS IE 5, it seems that it cannot handle cookies with domain name, path and time. This is something I discovered while designing the pages of this site.

The third limitation is on the client side. The maximum number of cookies that can be created by a browser is 30, and each cookie cannot exceed 4KB. The total number of cookies that can be set by each WEB site cannot exceed 20.

The above is all about the PHP cookie operation to be introduced in this section. We have introduced in detail the setting, use and deletion of cookies in PHP, as well as some issues to pay attention to. I hope to be helpful.