Guide to using cookies in PHP_PHP Tutorial-PHP Tutorial-php.cn

Summary
Cookie is a way for a server or script to maintain information on the client's workstation under the HTTP protocol. Cookies are small files saved on the user's browser by the Web server, which can contain information about the user (such as identification number, password, how the user purchases on the Web site or the number of times the user visits the site). Whenever a user connects to the server, the Web site can access the cookie information.
How to set cookies?
In PHP, you can use the setcookie function to set a cookie. Cookies are part of the HTTP headers, so the cookie function must be set before any content is sent to the browser. This restriction is the same as the header() function. Any cookie passed from the client will automatically be converted into a PHP variable. PHP obtains the information header and analyzes it, extracts the cookie name and turns it into a variable. Therefore, if you set a cookie such as setcookie("mycookie", "Cookies") php will automatically generate a variable named $mycookie with the value "Cookies".
Let’s take a look at the setcookie function syntax:
init setcookie(string CookieName, string CookieValue, int CookieExpireTime, path, domain, int secure);
Parameter description:
PATH: represents the location on the web server Directory, the default is the directory where the called page is located
DOMAIN: The domain name that the cookie can use, the default is the domain name of the called page. This domain name must contain two ".", so if you specify your top-level domain name, you must use ".mydomain.com"
SECURE: If set to "1", it means that the cookie can only be recognized by the user's browser It is remembered by a secure server.
Example of cookie usage
Suppose we have such a site that requires registration. It automatically identifies the user’s identity and performs related operations: If it is an already registered user, send him information ; If the user is not a registered user, a link to the registration page will be displayed.
According to the above requirements, we first create a database to save registered user information: first name, last name, email address, visit counter.
First create the table according to the following steps:
mysql＞ create database users;
Query OK, 1 row affected (0.06 sec)
mysql＞ use users;
Database changed
mysql＞ create table info (FirstName varchar(20), LastName varchar(40), email varchar(40), count varchar(3));
Query OK, 0 rows affected (0.05 sec)
Then create a php page Check cookies against database.
Since PHP can convert identifiable cookies into corresponding variables, we can check a variable named "myCookies":
　＜? if (isset($myCookies)) { // If the cookie already exists
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　}　　　　　　　　　　　　　　　　　　　　　　　　　　　 = } else { //If the cookie does not exist
, use the explode function to analyze into different variables, increase the counter, and set a new cookie:
$info = explode("&", $myCookies);
...
$count++;
$ CookieString=$FirstName.'&'.$LastName.'&'.$email.'&'.$count;
SetCookie ("myCookies",$CookieString, time()+3600); //Set cookies
Then use html statements to output user information.
Finally, update the database with the new counter value.
If this cookie does not exist, we display a link to the registration page (register.php).
The following register.php is the user registration page:
/* register.php */
＜form method="post" action="regOK.php"＞
First Name:＜input type ="text" name="FirstName"＞
　Last Name:＜input type="text" name="LastName"＞
　＜input type="submit" value="Register"＞
　＜/ form＞
The information filled in by the user on the register.php registration page is submitted to regOK.php:
/* regOK.php */
if ($FirstName and $LastName and $email) {
… ...//Query whether the user exists in the database
　}
　}else{
　……//Error handling
　}

The above program flow is as follows:
First check all Whether the information is filled in as required, if not, return and re-enter
If all the information is filled in, first, we retrieve the user login details from the database
Mysql_connect() or die ("Error connecting to the database!" );
$query="select * from info where FirstName='$FirstName' and LastName='$LastName' and email='$email'";
$result = mysql_db_query("users", $query );
　$info=mysql_fetch_array($result);
　$count=$info["count"]; Create a new cookie based on the information. If the same user does not have a database login, create a new database login and create a new cookie.
Now use the isset() function to check whether the user has a counter. If so, the counter will be incremented and a new cookie will be created:
$count++; //Increase the counter
$CookieString=$FirstName.'&'. $LastName.'&'.$email.'&'.$count;
SetCookie ("myCookies",$CookieString, time()+3600);
If there is no user counter, add one to mysql Record and set a cookie
Note: There should be no data output to the browser before calling the setcookie function, otherwise an error will occur.
How to implement cross-domain cookies?
According to the cookie specification, a cookie can only be used for one domain name. Therefore, if a cookie is set for one domain name in the browser, then this cookie will be used for other domain names. invalid.
Let’s talk about a cross-domain cookie implementation plan:
Step 1: Create a preset script
Add the following code to the preset script (or appear in the function before all scripts) .
　＜?php
　　 /*If the GET variable has been set, and it is different from the cookie variable
*Use the get variable (update cookie)
　　 */
　　global $HTTP_COOKIE_VARS, $HTTP_GET_VARS ;
if (isset($sessionid) && isset($HTTP_GET_VARS['sessionid']) && ($HTTP_COOKIE_VARS['sessionid'] != $HTTP_GET_VARS['sessionid'])) {
', $HTTP_GET_VARS['sessionid'], 0, '/', '');
$HTTP_COOKIE_VARS['sessionid'] = $HTTP_GET_VARS['sessionid']; '];
　　}　
　　?＞　
　After this code runs, a global variable 'sessionid' will be available to the script. It will save the sessionid value in the user's cookie, or the sessionid value sent through a GET request.
Step 2: Use variables for all cross-domain name references
Create a global configuration file to store the basic reference form of domain names that can be switched. For example, if we have domain1.com and domain2.com, the following settings would be:
　?php
;
　$domains['domain2'] = "http://www.domain2.com/-$sessionid-";
　　?＞　
　We write this piece of code:
　　?php
echo "Click ＜a href="", $domains['domain2'], "/contact/?email=yes"＞here＜/a＞ to contact us."; The code will produce the following output:
Click ＜a href="http://www.domain2.com/-66543afe6543asdf6asd-/contact/?email=yes"＞here＜/a＞ to contact us. ＜🎜 > Here the sessionid has been inserted into the URL.
Step 3: Configure Apache
Now, let’s configure Apache to rewrite this URL.
We need to change
http://www.domain2.com/-66543afe6543asdf6asd-/contact/
into this:
http://www.domain2.com/contact/?sessionid= 66543afe6543asdf6asd
And this url:
http://www.domain2.com/-66543afe6543asdf6asd-/contact/?email=yes
It becomes like this:
http://www.domain2. com/contact/?email=yes&sessionid=66543afe6543asdf6asd
In order to achieve the above requirements, simply configure two virtual servers as domain1 and domain2, as follows:
　VirtualHost ipaddress＞
　DocumentRoot /usr/local /www/domain1
ServerName www.domain1.com
RewriteEngine on
RewriteRule ^/-(.*)-(.*?.*)$ $2&sessionid=$1 [L, R, QSA]
RewriteRule ^/-(.*)-(.*)$ $2?sessionid=$1 [L, R, QSA]
/www/domain2
ServerName www.domain2.com
RewriteEngine on
RewriteRule ^/-(.*)-(.*?.*)$ $2&sessionid=$1 [L, R, QSA]
RewriteRule ^/-(.*)-(.*)$ $2?sessionid=$1 [L, R, QSA]
Write a request.

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