навчальний матеріал

Травень 2015
Автор: Анатолій, взято за навчальним ресурсом www.w3schools.com

Cookies and SESSION with PHP

Питання розділу

  1. What is a Cookie?
  2. Create Cookies With PHP
  3. Modify a Cookie Value
  4. Delete a Cookie
  5. What is a PHP Sessions?
  6. Get PHP Session Variable Values
  7. How does it work? How does it know it's me?
  8. Destroy a PHP Session

1. What is a Cookie?

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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setcookie(name, value, expire, path, domain, secure, httponly);
Parameter Description
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:



<?php
$cookie_name = "user";
$cookie_value = "John Doe";
setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/"); // 86400 = 1 day
?>

<?php
if(!isset($_COOKIE[$cookie_name])) {
echo "Cookie named '" . $cookie_name . "' is not set!";
} else {
echo "Cookie '" . $cookie_name . "' is set!<br>";
echo "Value is: " . $_COOKIE[$cookie_name];
}
?>

Note Note: The setcookie() function must appear BEFORE the <html> tag.
Cookie named 'user' is not set!



Modify a Cookie Value

To modify a cookie, just set (again) the cookie using the setcookie() function:

<?php
$cookie_name = "user";
$cookie_value = "Alex Porter";
setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/");
?>
<html>
<body>

<?php
if(!isset($_COOKIE[$cookie_name])) {
    echo "Cookie named '" . $cookie_name . "' is not set!";
} else {
    echo "Cookie '" . $cookie_name . "' is set!<br>";
    echo "Value is: " . $_COOKIE[$cookie_name];
}
?>

</body>
</html>


Delete a Cookie

To delete a cookie, use the setcookie() function with an expiration date in the past:

Example

<?php
// set the expiration date to one hour ago
setcookie("user", "", time() - 3600);
?>
<html>
<body>

<?php
echo "Cookie 'user' is deleted.";
?>

</body>
</html>


What is a PHP Sessions?

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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.

What is a PHP Session?

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.

Start a PHP Session

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>


Run example »

Get PHP Session Variable Values

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>





How does it work? How does it know it's me?

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.

Modify a PHP Session Variable

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>





Destroy a PHP Session

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>