To make the data accessible across the website we need to use session.

Session create a temporary file on the server where the registered data is stored and the data is made available to all pages.

The location of the temporary file is determined by a setting in the php.ini file called session.save_path.

When a session start

PHP first create a unique identifier for that particular session which is a random string of 32 hexadecimal number.

A PHPSESSID named cookie is called automatically and sent to the user computer to store unique session identification string.

A file is created automatically on the server in the designated temporary directory.

A PHP session is easily started by making a call to the session_start() function.

we can use the constant SID which is defined if the session started if the user do not allow to get cookie.

A session is closed when the user close the browser.

isset() function is used to check if the session is set already or not.

You do not need to call start_session() function to start a session if you can set session.auto_start variable to 1 in php.ini file.

The htmlspecialchars() can be used when printing the SID in order to prevent XSS related attack.