Skip to main content

What is Session Control/Variables?

What is Session Control/Variables?

In the post An Example of User Authentication System in PHP we created a simple authorization system which could show a personalized page when the user enters correct username and passwords. But since HTTP is a stateless protocol (it can’t figure out if two subsequent requests come from the same user) we cannot preserve the state (logged in) on ant consecutive clicks. All it means is that after logging in into that script, if the user clicks on some link, there is no way we can preserve the logged in state (know that a logged in user is requesting a page). Therefore we cannot, that way, personalize the whole site for the logged in user.

So, only logging in someone is not all, we’ve tpo preserve that state across the whole session. For this PHP gives us a easy-to-use method. We call it Session Control because it can help maintain a state throughout a session.

We implement Session Control using Session Variables whose values are preserved throughout a session. But before accessing or creating any session variable we need to begin a session with the help of the following code:

session_start();

After this we can register session variables like below:

$_SESSION['var']=1;

Above line of code will create a special variable ‘var’ having value 1. the speciality being that its value will be preserved across consecutive re quests to pages unless the session expires.

<?php
//start a session
session_start();
//create a session variable
$_SESSION['var']=1;
?>

And the following:

<?php
//start a session
session_start();
//display session varaible
echo $_SESSION['var'];
?>

Now if you request the first script followed by the second, the second one will have access to the variable set by the first one. The requesting of these two pages comprises a session and hence session variable ‘var’ is accessible to the second script. Do remember that the second script can access the session variable only if the first script was requested prior to it from the same computer and browser. If you close the browser or request the second page from other computer or browser without running the first script the session variable will not contain any value. What it means is that the client machine stores the session data.

So if ten computers set ten different session variables we may track and serve content to each of them separately and uniquely according to their authorization level. This is how ‘Actual’ User Login Systems work.

Just like starting a session, when you are through with the session acess you can close it using the following function:

session_destroy();

After invoking this no session variable will be accessible. This is what we know as logging out.

<?php
//start a session
session_start();
//display session varaible
echo $_SESSION['var'];
//destroy session
session_destroy();
//if you reload the page session
//variable will not be aceessible
//since that session was destroyed
?>

Some points to note:

  1. Session by default last until it is explicitly destroyed or when the browser is closed.

  2. Internally cookies on the client machine are used to store unique session identifier but actual session variables are stored on the server

Previous Articles:

Popular posts from this blog

Fix For Toshiba Satellite "RTC Battery is Low" Error (with Pictures)

RTC Battery is Low Error on a Toshiba Satellite laptop "RTC Battery is Low..." An error message flashing while you try to boot your laptop is enough to panic many people. But worry not! "RTC Battery" stands for Real-Time Clock battery which almost all laptops and PCs have on their motherboard to power the clock and sometimes to also keep the CMOS settings from getting erased while the system is switched off.  It is not uncommon for these batteries to last for years before requiring a replacement as the clock consumes very less power. And contrary to what some people tell you - they are not rechargeable or getting charged while your computer or laptop is running. In this article, we'll learn everything about RTC batteries and how to fix the error on your Toshiba Satellite laptop. What is an RTC Battery? RTC or CMOS batteries are small coin-shaped lithium batteries with a 3-volts output. Most laptops use

The Best Way(s) to Comment out PHP/HTML Code

PHP supports various styles of comments. Please check the following example: <?php // Single line comment code (); # Single line Comment code2 (); /* Multi Line comment code(); The code inside doesn't run */ // /* This doesn NOT start a multi-line comment block /* Multi line comment block The following line still ends the multi-line comment block //*/ The " # " comment style, though, is rarely used. Do note, in the example, that anything (even a multi-block comment /* ) after a " // " or " # " is a comment, and /* */ around any single-line comment overrides it. This information will come in handy when we learn about some neat tricks next. Comment out PHP Code Blocks Check the following code <?php //* Toggle line if ( 1 ) {      // } else {      // } //*/ //* Toggle line if ( 2 ) {      // } else {      // } //*/ Now see how easy it is to toggle a part of PHP code by just removing or adding a single " / " from th

How to Remove Bullet Points in CSS

This will be a short guide on how to remove bullet points from ordered/unordered lists with CSS, you only need two lines of CSS for this. The first removes the actual bullet points and the second one removes the space to the left, as evident from the following video: We'll also be doing some bullet beautification in the last section if that's what you are looking to do. How to Remove Bullet Points in HTML/CSS Now that we know what CSS properties actually accomplish what we want let's see how we can implement this in our HTML code. Using Inline "style" Tag (The quick and dirty way) As the title suggests, this is the quickest way to remove bullet points in which you wouldn't have to edit any CSS files (for example, for Blogger or WordPress). This method would be useful for a one-off case - just add the following " style " attribute to the list you want to remove the bullet points from: <h1>Ordered List</h1> <ol  style="list-styl