Today I had skype interview for a job as PHP developer, one of the questions asked was about Cookies and PHP Sessions.
The question was, can PHP session be set and read, used, if Cookies are disabled in users Browser?
I told them not, beacuse PHP Sessions by default depends on setting a session cookie. When PHP session starts, new session Cookie is set with default name PHPSESSID, and that cookie holds value of that session id, for example: ftu63d8al491s5gatuobj39gk7
Then on apache server in tmp folder file sess_ftu63d8al491s5gatuobj39gk7 is created and it holds content of that session, for example: test1|s:12:"SessionTest1";test2|s:12:"SessionTest2";
They told me that's not true, and that you can use PHP Sessions even if user disables cookies in his browser.
Then I told them that you can do that, but then session id would be passed through URL as GET variable. And that's not secure and you must set it up in php.ini.
They were talking how you can use PHP Sessions even if Cookies are disabled in browser. And what if we are building web shop, and some granny uses our web shop and disables cookies and she joust don't care. And that PHP Sessions are great because you can use them even if user disables Cookies. I was like wtf, wtf wtf?!?!
I made test with two files, index.php starts session and sets session variables. And then session.php tries to read that session variables.
This is how it looks:
index.php
<p>This is where I start and set php sessions.</p>
<?php
session_start();
$_SESSION['test1'] = "SessionTest1";
$_SESSION['test2'] = "SessionTest2";
?>
<p>This is a link, that starts new HTTP Request, and tries to read session set on this page:</p>
<p>Read Session</p>
session.php
<?php
session_start();
var_export($_SESSION);
?>
<p>Back</p>
Now, if you enable cookies in your browser, visit index.php, and the visit session.php , session would be printed out.
But, if you clear your browser history and cookies, and then visit index.php, and then visit session.php, you would see empty array right?
So basically my question is, am I right?
Can you use PHP sessions if you disable cookies in your browser?
And do PHP Session mechanism by default, depends on setting a session COOKIE?
Update:
I was going mad about this, so I called back the guy I was talking with. And asked him, can PHP session work without cookies by default? The guy said "yes". Then I told him he is wrong and he said: "yes, yes, if you say so..." and start laughing. Then I told him, ok if PHP session can work without setting cookie, how would server know current user/browser session id, if its not stored in a session cookie? (I wanted to see if he knows that session id can be passed as GET variable) And he was quiet for at least 20s, and told me that he is a System Administrator, and that I should ask that the Developer guy. And that he is 43 years old and has huge experience of 13 years in the bussines (he started with 30? wtf?), but he trusts me on this one. And I explained him how Session work and that you can use it without Cookie but then session id is passed as GET variable, and told him I told them that on interview, but they ware telling me no, no no... :S
So basically, the guy didn't have a clue about PHP and PHP Sessions, and yes he was the one that asked me about sessions telling me that PHP Session can work without cookie, even when I told him it cant be done, and that there is a way to use PHP Sessions without cookies but it won't work by default. He was like, no no no...
At the end he told me that he was thinking that sessions can work without cookies because he, as System Admin on his servers, can never see sessions in tmp folder?!?!?
Anyway, those guys suck at PHP, there is no way I will accept job offer from them, and after all this I dont think they will offer me a job anyway...
Thanks for all the comments!
"A visitor accessing your web site is assigned a unique id, the
so-called session id. This is either stored in a cookie on the user
side or is propagated in the URL. "
Sessions: Introduction
If session.use_cookies = 1 (Cookie enabled.)
If session.use_cookies = 0 (Cookie disabled.)
If session.use_cookies = 1 then session stores the sessionId into cookie. Calling session_id() get the stored sessionId from cookie and saved data into session array will be found on all the pages. If session.use_cookies = 0 In this case session does not store sessionId into cookie and you will get each time a new sessionId using session_id() and data stored into session on other pages will not be found on another pages.
Yes session will work when cookies is disabled.
But first apache check php configuration settings.
Like:
--enable-trans-sid
and
--enable-track-vars
if these value are set true the session will passed by POST automatically.
If "--enable-trans-sid" and "--enable-track-vars" values are set to FALSE, we need to pass session id by using the SID constant.
< a href="index.php?<?= SID ?>" >Navigate from here< /a >
Need to set php.ini
ini_set("session.use_cookies", 0);
ini_set("session.use_trans_sid", 1);
So basically my question is, am I right?
Mostly. In the real world: YES.
Can you use PHP sessions if you disable cookies in your browser?
You CAN use PHP sessions without cookies, as long as the browser identity is obtained somehow and yields a unique value (and this value is passed to the PHP session layer):
session ID in GET (which is the "standard" PHP way if cookies are not allowed, and the "other" way you described). This value is then propagated automatically by PHP, e.g. added to all A HREF's and so on. Where it is not propagated because the automagical link recognition failed (e.g. complex URL built in Javascript), it is your responsibility to provide accordingly.
Or - and here we're not in Kansas anymore:
passed among the nonces with Auth Digest (this is a dirty trick, and of course requires that the whole site is behind an Auth-Digest access authentication scheme. And you can no longer use a "dummy auth" (i.e. http://welcome:guest#www.example.com ) because some browsers, e.g. Internet Explorer, do not support them anymore for security reasons)
recognizing the browser some other way ("fingerprinting") (this is normally(1) suicidal)
Use LSO (Local Shared Objects) to generate a random UUID if it's not there already, and store it so that it can be retrieved on subsequent accesses.
other ways ( see http://en.wikipedia.org/wiki/Evercookie )
(1) if you were in a LAN where you can trust the IPs, you could associate a "session" to the user IP. You might enforce a strict "no cookies" policy in a small firm and still have user sessions without resorting to _GET/_POST for your session ID.
You are right, Session cannot work without cookies.
To illustrate this try doing the following actions.
Login To Gmail.
After login disabled the cookies.
Refresh the page.
You will be redirected to the login page again as the server cannot identify the session.
Now again enable the cookies.
Refresh the page. (Note: Don't click on login button).
You will be automatically redirected to the Gmail inbox.
Hence, we can say without cookies session will not work.
Also, If you are trying to login into the gmail( taking as example you can take any website) with diabled cookies then it will message as "Your browser has cookies disabled. Make sure your cookies are enabled and try again."
If it was me, I would say "Yes"
Since you could store session in form / url somewhere to passed to next page (very bad idea). So, based on his question "can PHP session be set and read, used, if Cookies are disabled in users Browser?"
Then, it should be yes. It can read and used.
However, If user close browser, then it's gone, and that's it. (since that guy didn't ask about this part)
Yes.. It will Work
1.PHP will pass one GET parameter in URL with the name PHPSESSID but it can be changed session.name in php.ini file.
2. It add one hidden input in forms with same name.
You will need to put the session ID in the URL. You will need to make a change in your php.ini file so if you are on a shared host you will need to contact them to see what they will do for you.
// tell the PHP we want to use cookies from the session
ini_set('session.use_cookies', '0');
ini_set('session.use_only_cookies', '0');
ini_set('session.use_trans_sid','1');
session_start();
// then pass the session ID in the URL(inspect, navigate the network refresh the page you will see in the headers your session ID)
So I created this little login system for my php site, I have a login form where I first create the session with a few session variables like UserId and such.
I also do session_destroy() before i create the session so that any existing session will be destroyed.
Then I have this php file that I include on the top of every page on my site which opens that session with session_start() and starts the mysql connection and such.
Problem is, on some pages the session does open correctly and on other pages seems to create a new session. In fact if I go to another page and return to the page where the correct session isn't opening it's the same incorrect session, so I actually have two sessions opened it seems...
When I echo the session ID on page where it works and the one where it doesnt, they have different session ID's so I'm confused.
First of all don't use session_destroy() as it will delete the session on the next page request. Instead use:
unset( $_SESSION ); //this will delete the session immediately
To try and test the problem use the session_id() function:
<?php
$a = session_id();
if(empty($a)) session_start();
echo "SID: ".SID."<br>session_id(): ".session_id()."<br>COOKIE: ".$_COOKIE["PHPSESSID"];
?>
IF you are getting duplicate cookies (as is in this case), check the domain and path of each cookie. Make sure the cookie path are domain are always set to the same domain and path is always the root of your website (assuming you want the cookies site-global).
Each cookie is visible to the set path and domain, all paths starting with the path set, and may be set to match all subdomains of the domain.
Based on the comments to the question.
I need to transfer the session value in one browser to another browser in my web site
For example from Firefox to Google Chrome
It is impossible to transfer a PHP $_SESSION variable or any other value between browsers, even with JS.
If your website contains a login, you could attach information to that login in a database and retrieve it when a user logs in using another browser.
You could set your own cookies with a session id and use a shared session database for all of your domains. This would require some legwork in implementing your own sessions.
Cross-Domain Cookies
I use OAuth to authenticate at an external website. Everything is okay but the session variable misses after redirecting from external websites.
Summary:
I store a session var in my website then go to login page of other website. After logging in and confirming, it redirects to my callback, when I check the previous session var, it misses! How to fix it?
I tried to call session_start() everywhere I use session but it doesn't work. Of course I enabled session in "php.ini" and enabled cookie in browser. :) I debugged but can't find the reason out.
Update:
After storing my session var, I do a request like this:
http://mixi.jp/connect_authorize.pl?oauth_callback=http%3A%2F%2Fmypage.com%2Fcallback.php&oauth_token=fjdklsfjlksd
Note the oauth_callback, it is the redirect URL. I don't know what mixi.jp use to redirect.
Make sure your site's domain is 100% identical before and after the redirection.
Note that
www.yoursite.com
and
yoursite.com
are two different sites cookie-wise.
The session id is stored in a cookie. The cookie is send in every page of the domain you registered in. Whe you jump to another domain, your cookie with the session id is not send. You must pass the session id to your new domain and then create a new cookie in this domain with the session id.
header('Location:redirect.php?session=' . session_id());
And then in the redirected page restore the session
<?php
session_id($_GET['session']);
session_start();
I have 2 pages: login.php and index.php. Both pages start with
session_start();
When I set
$_SESSION['user'] = "name";
in login.php and than open index.php, my session object is empty. How come?
EDIT:
I found the problem: IE 7. I had to grand access to my domain. However, I thought a session is stored on the server, instead of the client? Than why do I have IE grand access to my domain? (http://www.pcwindowstips.com/2007/09/04/how-to-enable-cookies-in-internet-explorer-7/)
I thought a session is stored on the server, instead of the client? Than why do I have IE grant access to my domain? (http://www.pcwindowstips.com/2007/09/04/how-to-enable-cookies-in-internet-explorer-7/)
The way sessions work is that a session cookie is stored for the site, which contains your session ID. The only way the server knows who you are is when it reads the session ID cookie on every page load. All of the $_SESSION data is stored on the server for each user, but the cookie must be set for the server to know which $_SESSION data to retrieve.
This is also why you can essentially "become" another user if you obtain their session id cookie.
Internet Explorers have a stricter cookie policy than most other browsers. Check your session cookie parameters (see also session_get_cookie_params()) and try to replace the default values by explicit values where possible. Additionally you might send a [fake P3P policy](http://msdn.microsoft.com/en-us/library/ms537343(VS.85).aspx) to satisfy the Internet Explorers.
Perhaps this variable in php.ini is mapping to an existing path
session.save_path = "c:/wrong/path"
Here is something that happened to me that might shed light for someone. My session wasn't working properly. IE 8 and Firefox were losing the session information.
I included a file. That included file had an extra carriage return after the trailing &ques?>
That carriage return started the session. I put session_start after the include. BOOM.
Not much info here, I'll try to use my psychic powers.
After the user logs in, do you set the session var and then redirect the user to index.php using an http header? If so, I don't think the session cookie gets sent to the user. If that is the case, the solutions are:
call session_start() when the login form is initially displayed (not just after the user posts back to it); or:
display a "login successful!" message and then redirect with a meta-refresh, or just provide a link to index.php.
You can also try to dump the session ID on both pages, to see if you are somehow starting a new session:
echo 'Session ID is: ' . SID . "<br/>\n"
You need verify if the cookies are enabled and nothing ( this includes blank lines in the beginning or in the end of archive) sent to browser before you call session_start().