Detailed tutorial on using PHP Cookie_PHP tutorial

1. Set Cookie
PHP uses the SetCookie function to set Cookie. One thing that must be noted is that cookies are part of the HTTP protocol header and are 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:

int SetCookie(string name, string value, int expire, string path, string domain, int secure);
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 in the page that is set, and the browser will not see it until the next page. The reason why the cookie can be removed from the client's machine and sent back to the server.
Setting cookies on the same page is actually from back to front, so if you want to delete a cookie before inserting a new one, you must first write the insertion statement, and then write the deletion statement, otherwise there may be inaccuracies. desired results.
Let’s look at a few examples:
Simple:
SetCookie("MyCookie", "Value of MyCookie");
With expiration time:
SetCookie("WithExpire", "Expire in 1 hour", time()+3600);//3600 seconds=1 hour
Everything is available:
SetCookie("FullCookie", "Full cookie value", time()+3600, "/forum", ".phpuser.com", 1);

There is another point to note here. For example, your site has several different directories. So if you only use cookies without a path, the cookies set in a page in one directory will not be visible in a page in another directory. In other words, cookies are path-oriented. In fact, 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. The way to solve this problem is to add the path and domain name when calling SetCookie. The format of the domain name can be "www.phpuser.com" or ". phpuser.com".
The part representing the value in the SetCookie function will be automatically encoded when passed. In other words, if the value of the value is "test value", it will become "test%20value" when passed, the same as the URL method. . Of course, this is transparent to the program, because PHP automatically decodes the cookie value when it receives it.

If you want to set multiple cookies with the same name, use an array. The method is:
SetCookie("CookieArray[]", "Value 1");
SetCookie("CookieArray[]", "Value 2");
or
SetCookie("CookieArray[0]", "Value 1");
SetCookie("CookieArray[1]", "Value 2");

2. Receiving and processing Cookies
PHP has very good support for receiving and processing Cookies. It is completely automatic, just like the principle of 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 cookie. value. The same applies to arrays. Another way is to reference PHP's global variable $HTTP_COOKIE_VARS array.
Examples are as follows: (assuming these have been set in previous pages and are still valid)
echo $MyCookie;
echo $CookieArray[0];
echo count($CookieArray) ;
echo $HTTP_COOKIE_VARS["MyCookie"];
It’s that simple.

3. Delete Cookie
To delete an existing cookie, there are two ways:

One is to call only with SetCookie of the name parameter, then the cookie named this name will be deleted from the related user computer;
Another way is to set the cookie expiration time to time() or time()-1, then the cookie will be on this page After browsing, it was deleted (actually it became invalid).
It should be noted that when a cookie is deleted, its value is still valid on the current page.

4. Restrictions on using cookies
First of all, it must be set before the content of the HTML file is output;
Secondly, different browsers have different restrictions on cookies. Handling inconsistent terms and sometimes erroneous results. 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.