A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user's computer. Each time the same computer requests a page with a browser, it will send the cookie too. With PHP, you can both create and retrieve cookie values.
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|name||Required. Specifies the name of the cookie|
|value||Optional. Specifies the value of the cookie|
|expire||Optional. Specifies when the cookie expires. The value: time()+86400*30, will set the cookie to expire in 30 days. If this parameter is not set, the cookie will expire at the end of the session (when the browser closes)|
|path||Optional. Specifies the server path of the cookie. If set to "/", the cookie will be available within the entire domain. If set to "/php/", the cookie will only be available within the php directory and all sub-directories of php. The default value is the current directory that the cookie is being set in|
|domain||Optional. Specifies the domain name of the cookie. To make the cookie available on all subdomains of example.com, set domain to ".example.com". Setting it to www.example.com will make the cookie only available in the www subdomain|
|secure||Optional. Specifies whether or not the cookie should only be transmitted over a secure HTTPS connection. TRUE indicates that the cookie will only be set if a secure connection exists. Default is FALSE.|
The following example creates a cookie named "user" with the value "John Doe". The cookie will expire after 30 days (86400 * 30). The "/" means that the cookie is available in entire website (otherwise, select the directory you prefer). We then retrieve the value of the cookie "user" (using the global variable $_COOKIE). We also use the isset() function to find out if the cookie is set:
|Note: The setcookie() function must appear BEFORE the <html> tag.|
To modify a cookie, just set (again) the cookie using the setcookie() function:
To delete a cookie, use the setcookie() function with an expiration date in the past:
A session is a way to store information (in variables) to be used across multiple pages.
Unlike a cookie, the information is not stored on the users computer.
When you work with an application, you open it, do some changes, and then you close it. This is much like a Session. The computer knows who you are. It knows when you start the application and when you end. But on the internet there is one problem: the web server does not know who you are or what you do, because the HTTP address doesn't maintain state.
Session variables solve this problem by storing user information to be used across multiple pages (e.g. username, favorite color, etc). By default, session variables last until the user closes the browser.
So; Session variables hold information about one single user, and are available to all pages in one application.
A session is started with the session_start() function.
Session variables are set with the PHP global variable: $_SESSION.
Now, let's create a new page called "demo_session1.php". In this page, we start a new PHP session and set some session variables:
<?php // Start the session session_start(); ?> <!DOCTYPE html> <html> <body> <?php // Set session variables $_SESSION["favcolor"] = "green"; $_SESSION["favanimal"] = "cat"; echo "Session variables are set."; ?> </body> </html>
Next, we create another page called "demo_session2.php". From this page, we will access the session information we set on the first page ("demo_session1.php").
Notice that session variables are not passed individually to each new page, instead they are retrieved from the session we open at the beginning of each page (session_start()).
Also notice that all session variable values are stored in the global $_SESSION variable:
<?php session_start(); ?> <!DOCTYPE html> <html> <body> <?php // Echo session variables that were set on previous page echo "Favorite color is " . $_SESSION["favcolor"] . ".<br>"; echo "Favorite animal is " . $_SESSION["favanimal"] . "."; ?> </body> </html>
Another way to show all the session variable values for a user session is to run the following code:
<?php session_start(); ?> <!DOCTYPE html> <html> <body> <?php print_r($_SESSION); ?> </body> </html>
Most sessions set a user-key on the user's computer that looks something like this: 765487cf34ert8dede5a562e4f3a7e12. Then, when a session is opened on another page, it scans the computer for a user-key. If there is a match, it accesses that session, if not, it starts a new session.
To change a session variable, just overwrite it:
<?php session_start(); ?> <!DOCTYPE html> <html> <body> <php // to change a session variable, just overwrite it $_SESSION["favcolor"] = "yellow"; print_r($_SESSION); ?> </body> </html>
To remove all global session variables and destroy the session, use session_unset() and session_destroy():
<?php session_start(); ?> <!DOCTYPE html> <html> <body> <?php // remove all session variables session_unset(); // destroy the session session_destroy(); ?> </body> </html>