PHP and MySQL basic tutorial (3)_PHP tutorial

Using cookies to track and identify users

Let’s take a look at the content saved in the browser. If you are using IE5, there is a cookies 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 are 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 its previously set cookies to Amazon before accepting the first page. Then Amazon.com checks the content sent to see if there is relevant information in the database. After matching, it creates a customized page for me and sends it over.
Assign a value to cookies
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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 < HEAD> tag:

< ?php

setcookie("CookieID", $USERID);

?>

< HTML>

< BODY>

< /BODY>

< /HTML>

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 cookie, usually a string variable, for example: $USERID. You can also assign it a ?? 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 this session. This parameter can be an absolute time, represented by DD-Mon-YY HH:MM:SS, such as: "24-Nov-99 08:26:00". 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 this cookie can only be sent over "secure" networks. 0 or omitted means any type of network is acceptable.
Cookies and Variables
Author: Yangmei Compilation Number of clicks on this article: 127

When the PHP script extracts a cookie from the client's browser, it will automatically convert 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 each user
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Go back and take a look at the submitform.php3 file above. , its function is to add the customer's name to the database, and 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 every time a user visits my website, I can know who he is through the cookie and the user ID in it. .

MySQL can be set to automatically assign a number to each new record. This number starts from 1 and automatically increases by 1 each time thereafter. With one line of SQL statements, you can easily add such a field to the data table. I call it USERID:

ALTER TABLE dbname

ADD COLUMN

USERID INT (11) NOT NULL

PRIMARY KEY AUTO_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 "NOT NULL" keyword to prevent the value of this field from being NULL; then use "PRIMARY KEY" to set it as an index field, so The search 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:

< ?php

mysql_connect (localhost, username, password);



mysql_select_db (dbname);

mysql_query ("INSERT INTO tablename (first_name, last_name)

VALUES ('$first_name', '$last_name')

") ;

setcookie("CookieID",

mysql_insert_id(),

time()+94608000,

"/"); /* Three years The cookie will expire */

?>

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
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Us Let's write a script like what Amazon.com does. First, the PHP script checks to see if a cookie was sent by the client's browser. If so, the user's name will be displayed. If the cookie is not found, display a form to ask the customer to register their name, then add it to the database and set the cookie while the customer is browsing.

First, let’s display the cookie content:

< ?php

print $CookieID;

?>

Then, you can display the name:

< ?php

mysql_connect (localhost, username, password);



mysql_select_db (dbname );



$selectresult = mysql_query ("SELECT * FROM tablename

WHERE USERID = '$CookieID'

");

$row = mysql_fetch_array($selectresult);

echo "Welcome", $row[first_name], "!";

?>

That's it. I have no judgment in it, leave it to you to complete it