Using Sessions in PHP

Session variables hold information about one single user, and are available
to all pages in one application.

over internet to maintain state of the user we will use sessions, sessions are
temporary, by a unique id web server will keep the user data in the web server
with which user state can be maintained across the pages in the website.

before we start using the session variables  we have to start the
session with

session_start()

note:we have to start the session before the beginning of static HTML

Once we start the session then  playing with session is easy

Creating Session Variable

To create Session variable

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$_SESSION[variablename]=value of the session variable
 
//$_SESSION['username']="supreme";

Retrieving Session Variable

To retrieve Session variable

targetvariable=$_SESSION[variable];

ex: user=$_SESSION["username"];

A sime Program usingSession (Refresh.php)

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<?php
  session_start();
 
if (isset($_SESSION["refresh"]))
 $_SESSION["refresh"]=date("Y-m-d H:i:s A",time());
echo "You Came to this Page at : ".$_SESSION["refresh"]."<br>Now, Current  Time  is ".date("Y-m-d H:i:s A",time());
?>

paste this code as refresh.php  and refresh the page and you will come to
know the difference

Its always better to check  and  use the session variable like with
isset function we can  know weather the session variable is available or
not.If session variable exists we can start using it otherwise assaign it and
then go for it.

ex: the same way  in the above  refresh.php page

Clearing the Session variables

we can clear either single session variable or we can destroy the total
session

unlike cookies, we have unset function to  clear the session variables

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 unset($_SESSION["session_variable_name"])

this will be used when  you want to clear one particular  session
variable

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 unset($_SESSION["refresh"]);

to destroy current session totally

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session_destroy();
 
 
//ex: session_destroy();