Use cookies in php to track and identify users

Let's take a look at what's saved in the browser. If you are using IE5, there is a cookie directory in the windows directory. There are many text files in it. The file names are similar to wudong@15seconds[1].txt. These are the cookies used by the browser to save values. . In previous versions of IE, the contents of cookies were viewable, but now the contents have been encoded. Before the browser gets a Web page, it will first check whether the domain name of the page exists in the cookie. If there is a match, the browser will first send the matching cookie to the server, and then accept and process the cookie sent by the server. page.

Let’s take an example of cookie application: when I connect to Amazon.com, the browser will send the contents of the cookies it previously set to Amazon before accepting the first page. Then Amazon.com checks the transmitted content to see if there is relevant information in the database. After matching, it creates a customized page for me and transmits it.
Assign values ​​to cookies

Cookies must be assigned a value before the server sends any content to the client's browser. To do this, the cookie settings must be placed within the tag:
​setcookie("CookieID",$USERID);
​?>




The setcookie function has a total of six parameters, separated by commas:

The name of the cookie is a string, for example: "CookieID". Colons, commas and spaces are not allowed in between. This parameter is required, while all other parameters are optional. If only this parameter is given, the cookie will be deleted.

The value of the cookie is usually a string variable, such as $USERID. You can also assign a ?? to it to skip setting the value.

The time when the cookie expires. If omitted (or assigned a value of zero), the cookie will expire at the end of the session. This parameter can be an absolute time, represented by DD-Mon-YYHH:MM:SS, for example: "24-Nov-9908:26:00". What is more commonly used is to set a relative time. This is achieved through the time() function or the mktime function. For example, time()+3600 will cause the cookie to expire after one hour.

A path used to match cookies. When there are multiple cookie settings with the same name on a server, this parameter is used to avoid confusion. Using the "/" path has the same effect as omitting this parameter. It should be noted that Netscape's cookie definition puts the domain name in front of the path, while PHP does the opposite.

The domain name of the server is also used to match cookies. It should be noted that a dot (.) must be placed before the domain name of the server. For example: ".friendshipcenter.com". Because unless there are more than two points, this parameter cannot be accepted.

The security level of the cookie is an integer. 1 means that this cookie can only be sent over "secure" networks. 0 or omitted means any type of network is acceptable.

​Cookies and variables

When the PHP script extracts a cookie from the client's browser, it automatically converts it into a variable. For example: a cookie named CookieID will become the variable $CookieID.

The content of Cookies is reported to be stored in the HTTP_COOKIE_VARS array. You can also access the specified cookie value through this array and the name of the cookie:

PRint$HTTP_COOKIE_VARS[CookieID];

​Remember every user

Let’s look back at the submitform.php3 file above. Its function is to add the customer’s name to the database. Now I want to add something to it. I want to assign a unique user ID to each user, and then put this ID in Cookies, so that whenever a user visits my website, I can know who he is through the cookie and the user ID in it. .

MySQL can be set up to automatically assign a number to each new record. This number starts at 1 and automatically increases by 1 each time thereafter. With one line of SQL statement, you can easily add such a field to the data table. I call it USERID:
ALTERTABLEdbname
ADDCOLUMN
USERIDINT(11)NOTNULL
​PRIMARYKEYAUTO_INCREMENT;

We have made some special settings for this field. First, define its type as an 11-bit integer through "INT(11)"; then use the "NOTNULL" keyword to prevent the value of this field from being NULL; then use "PRIMARYKEY" to set it as an index field, so that it can be searched will be faster; finally, "AUTO_INCREMENT" defines it as an automatically incremented field.

Once the user's name has been inserted into the database, it's time to set a cookie on their browser. What is used at this time is the value of the USERID field we just talked about:

​mysql_connect(localhost,username,passWord);
​mysql_select_db(dbname);
mysql_query("INSERTINTOtablename(first_name,last_name)
VALUES('$first_name','$last_name')
");
​setcookie("CookieID",
​mysql_insert_id(),
time()+94608000,
"/");/*The cookie will expire after three years*/
​?>

The PHP function mysql_insert_id() returns the value of the field defined by AUTO_INCREMENT after the last INSERT query was executed. In this way, as long as you don’t clear your browser’s cookies, the website will “remember” you forever

Read cookies

Let's write a script like what Amazon.com does. First, the PHP script will check whether the client's browser has sent a cookie. If so, the user's name will be displayed. If the cookie is not found, a form is displayed asking the customer to register their name, then added to the database and the cookie is set while the customer is browsing.

​First, let’s display the content of the cookie:
​print$CookieID;
​?>
Then, the name can be displayed:
​mysql_connect(localhost,username,password);
​mysql_select_db(dbname);
​$selectresult=mysql_query("SELECT*FROMtablename
​WHEREUSERID='$CookieID'
");
​$row=mysql_fetch_array($selectresult);
echo "Welcome",$row[first_name],"!";
​?>
That’s it. I have no judgment in it and leave it to you to complete it

The above has introduced the use of cookies in PHP to track and identify users, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.