PHP Session and Variable Handling Functions. Free online PHP and MySQL Web Database Programming Tutorial...

In this lesson we will learn some very useful functions for session handling and variable handling.

Session-Handling Functions
Session handling is a way of perserving or persisting the session data of a user as a he / she navigates our Web site. The session data could be variables or objects.

session_start()
The session_start() function denotes the start a session if one has not already been started, or it resumes a session if there already exists a session. This function is argumentless i.e. it takes no arguments. This function has to be called at the beginning of the PHP script. Its syntax follows:

session_start();

session_destroy()
We use the session_destroy() function to destroy all the variables and other data associated with a user session. This functin is also argumentless and takes no arguments. Its syntax follows:

session_destroy(); Variable Handling Functions
Variable handling functions isset() and unset() help us manage our variables within the scope of a web application:

isset()
We use the isset() function to determine whether the argument variable exists. The isset() function returns true if the variable exists and false otherwise. Its syntax follows:

isset(var);

unset()
We use the unset() function to destry the argument variable. Its syntax follows:

unset(var);

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