Difference between revisions of "PHP Session"
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Revision as of 19:50, 15 September 2017
PHP Session Variables 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. The code below should be at the very start of every page: <?php // Start the session session_start(); ?>
Set PHP Session Variable Values Session variables are set with the PHP global variable: $_SESSION: <?php // Set session variables $_SESSION["favcolor"] = "green"; $_SESSION["favanimal"] = "cat"; echo "Session variables are set."; ?>
Get PHP Session Variable Values
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 using
‘session_start()’. This should be at the very start of the page.
Also notice that all session variable values are stored in the global $_SESSION
variable. You retrieve a session value using the name given:
<?php
session_start();
?>
<!DOCTYPE html>
<html>
<body>
<?php
// Echo session variables that were set on previous page
echo "Favorite color is " . $_SESSION["favcolor"] . ".
";
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>
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>
