PHP Sessions And Cookies
PHP 5 Session : 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.
PHP 5 Cookies : A cookie is often used to identify a user.
What is a PHP Session and Cookies?
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.
Cookies : 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.
Start a PHP Session
A session is started with the session_start() function.
Session variables are set with the PHP global variable: $_SESSION.
Now, let's create a new page called "demo_session1.php". In this page, we start a new PHP session and set some session variables:
<?php
// Start the sessionsession_start();
?>
<!DOCTYPE html>
<html>
<body>
<?php
// Set session variables$_SESSION["favcolor"] = "green";
$_SESSION["favanimal"] = "cat";
echo "Session variables are set.";
?>
</body>
</html>
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 pageecho "Favorite color is " . $_SESSION["favcolor"] . ".<br>";
echo "Favorite animal is " . $_SESSION["favanimal"] . ".";
?>
</body>
</html>
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 variablessession_unset();
// destroy the session session_destroy();
?>
</body>
</html>
Now Let Us Concentrate For Cookies
Create Cookies With PHP
A cookie is created with the setcookie() function.
Syntax
setcookie(name, value, expire, path, domain, secure, httponly);
Only the name parameter is required. All other parameters are optional.
PHP Create/Retrieve a Cookie
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, $cookie_value, time() + (86400 * 30), "/"); // 86400 = 1 day?>
<html>
<body>
<?php
if(!isset($_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>
Output:
Cookie named 'user' is not set!
Note: You might have to reload the page to see the value of the cookie.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:
<?php
// set the expiration date to one hour agosetcookie("user", "", time() - 3600);
?>
<html>
<body>
<?php
echo "Cookie 'user' is deleted.";
?>
</body>
</html>
Check if Cookies are Enabled
The following example creates a small script that checks whether cookies are enabled. First, try to create a test cookie with the setcookie() function, then count the $_COOKIE array variable:
<?php
setcookie("test_cookie", "test", time() + 3600, '/');
?>
<html>
<body>
<?php
if(count($_COOKIE) > 0) {
echo "Cookies are enabled.";
} else {
echo "Cookies are disabled.";
}
?>
</body>
</html>
Output :
Cookies are enabled.
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