PHP sessions

#1
Csabi

Posted 05 December 2010 - 01:48 AM

Learning Programmer

Members
62 posts

Sessions can transfer data between two or more pages. It`s somehow like a variable that keep`s it`s value even if you call it from an another file. Let`s say that we have a website and in the index.php file we are asking for the name of the visitor and we store it in the $name variable (e.g.:$name = 'Tom').
If the visitor navigates to an another page the value of $name will be lost, so we would need to ask for the name on each page so in this case is way better to use sessions.

In order to use a session first we need to "start" it:

<?php

session_start();

?>

NOTE: The session_start(); function must be the at the very beginning of your code, even before the <html> tag.

A session variable look`s and works like an element of an associative array:

$_SESSION['name'] = 'Tom';

echo $_SESSION['name'];

And because sessions are keeping their value even if you go to an another page:
page1.php

<?php

session_start();

$_SESSION['name'] = 'Tom';

?>

page2.php

<?php

session_start();

echo $_SESSION['name'] ;

?>

Will output

Tom

Let`s say that we have a page that is displayed only to members. If somebody is logged in than it`s username is stored in a session. In order to show the content of the page to the visitor we need to check if the username session exists or not. This can be easily done using this function:

isset($_SESSION['username']); //Returns True if exists and False if not

So if we use the isset function our code will look like this:

<?php

session_start();

if(isset($_SESSION['username'])){

echo 'Welcome ' . $_SESSION['username'];

}

else{

echo 'You are not logged in!';

}

?>

When the user leaves your website or closes the browser the sessions are automatically deleted, but if you want to delete a session yourself use the following code:

unset($_SESSION['username']);

This is useful when you want to delete only a single session.

If you want to delete all the sessions use the following code:

session_destroy();

NOTE: After this function you can`t use more sessions on the page.

Example of using the session_destroy(); function:
log-out.php

session_start();

session_destroy();

By destroying the sessions the user is logged out.
Here is the original tutorial: php sessions
This is what you need to know about sessions... If you have any questions please ask me! :w00t:

Edited by Csabi, 06 December 2010 - 11:46 AM.

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#2
renu

Posted 21 December 2010 - 06:23 AM

Newbie

Members
2 posts

can i use session to unlimited pages?
if yes then how?

#3
Csabi

Posted 21 December 2010 - 07:09 AM

Learning Programmer

Members
62 posts

Yes, you just need to start sessions (session_start(); ) on each page

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#4
oldbrown

Posted 07 February 2011 - 05:36 PM

Newbie

Members
3 posts

I am very new to php, wondering if you could assist. Once a new member registers. Example: Bob registers through the registration form to my site, he then logs in. How do I use the session variable to to allow bob access to "Bobs" page without other registered users access to bobs page? Any assistance would be greatly appreciated

#5
Alexander

Posted 07 February 2011 - 07:41 PM

It's Science!

Moderators
4,124 posts

Location:Vancouver, Eh! Cleverness: 200

oldbrown said:

How do I use the session variable to to allow bob access to "Bobs" page without other registered users access to bobs page?

On the profile page you can check this quite easily, for example when you access profile.php?profile=bob

if(isset($_GET['profile']) {
    //You can check here if the profile exists, I have left this out
    if(isset($_SESSION['name']))
        if($_GET['profile'] == $_SESSION['name']) {
            echo "Welcome to " . htmlspecialchars($_GET['profile']) . "'s page!"
            // Then get information for profile
            // mysql_query("SELECT info FROM users WHERE name = '" . mysql_real_escape_string($_GET['bob']) . "'";
        } else {
            echo "You are not " . htmlspecialchars($_GET['profile']) . "." ;
        }
    } else {
        echo "You are not logged in.";
    }
} else {
    echo "You have not selected a profile.";
}

This is a very simplistic example.

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