PHP 5 Sessions

An alternative way to make data accessible across the various pages of an entire website is to use a PHP Session. A session creates a file in a temporary directory on the server where registered session variables and their values are stored. This data will be available to all pages on the site during that visit.

The location of the temporary file is determined by a setting in the php.ini file called session.save_path. Before using any session variable make sure you have setup this path.

PHP first creates a unique identifier for that particular session which is a random string of 32 hexadecimal numbers such as 3c7foj34c3jj973hjkop2fc937e3443.

A cookie called PHPSESSID is automatically sent to the user's computer to store unique session identification string

A file is automatically created on the server in the designated temporary directory and bears the name of the unique identifier prefixed by sess_ ie sess_3c7foj34c3jj973hjkop2fc937e3443.

When a PHP script wants to retrieve the value from a session variable, PHP automatically gets the unique session identifier string from the PHPSESSID cookie and then looks in its temporary directory for the file bearing that name and a validation can be done by comparing both values.

A session ends when the user loses the browser or after leaving the site, the server will terminate the session after a predetermined period of time, commonly 30 minutes duration.

Start a PHP Session

A session is started with the session_start() function. Session variables are set with the PHP global variable: $_SESSION.

Example -

<?php // Start the session session_start(); ?> <?php // Set session variables $_SESSION["favcolor"] = "green"; $_SESSION["favanimal"] = "cat"; echo "Session variables are set."; ?>

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Get PHP Session Variable Values

Example -

<?php session_start(); ?> <?php // Echo session variables that were set on previous page echo "Favorite color is " . $_SESSION["favcolor"] . ".<br>"; echo "Favorite animal is " . $_SESSION["favanimal"] . "."; ?>

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Modify a PHP Session Variable

Example -

<?php session_start(); ?> <?php // to change a session variable, just overwrite it $_SESSION["favcolor"] = "yellow"; print_r($_SESSION); ?>

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