What is the distinction between Sessions and Cookies in PHP?
A cookie is a bit of data stored by the browser and sent to the server with every request.
A session is a collection of data stored on the server and associated with a given user (usually via a cookie containing an id code)
Cookies are used to identify sessions. Visit any site that is using cookies and pull up either Chrome inspect element and then network or FireBug if using Firefox.
You can see that there is a header sent to a server and also received called Cookie. Usually it contains some personal information (like an ID) that can be used on the server to identify a session. These cookies stay on your computer and your browser takes care of sending them to only the domains that are identified with it.
If there were no cookies then you would be sending a unique ID on every request via GET or POST. Cookies are like static id's that stay on your computer for some time.
A session is a group of information on the server that is associated with the cookie information. If you're using PHP you can check the session.save_path location and actually "see sessions". They are either files on the server filesystem or backed in a database.
The main difference between a session and a cookie is that session data is stored on the server, whereas cookies store data in the visitor’s browser.
Sessions are more secure than cookies as it is stored in server. Cookie can be turned off from browser.
Data stored in cookie can be stored for months or years, depending on the life span of the cookie. But the data in the session is lost when the web browser is closed.
Cookie
is a small amount of data saved in the browser (client-side)
can be set from PHP with setcookie and then will be sent to the client's browser (HTTP response header Set-cookie)
can be set directly client-side in Javascript: document.cookie = 'foo=bar';
if no expiration date is set, by default, it will expire when the browser is closed.
Example: go on http://example.com, open the Console, do document.cookie = 'foo=bar';. Close the tab, reopen the same website, open the Console, do document.cookie: you will see foo=bar is still there. Now close the browser and reopen it, re-visit the same website, open the Console ; you will see document.cookie is empty.
you can also set a precise expiration date other than "deleted when browser is closed".
the cookies that are stored in the browser are sent to the server in the headers of every request of the same website (see Cookie). You can see this for example with Chrome by opening Developer tools > Network, click on the request, see Headers:
can be read client-side with document.cookie
can be read server-side with $_COOKIE['foo']
Bonus: it can also be set/get with another language than PHP. Example in Python with "bottle" micro-framework (see also here):
from bottle import get, run, request, response
#get('/')
def index():
if request.get_cookie("visited"):
return "Welcome back! Nice to see you again"
else:
response.set_cookie("visited", "yes")
return "Hello there! Nice to meet you"
run(host='localhost', port=8080, debug=True, reloader=True)
Session
is some data relative to a browser session saved server-side
each server-side language may implement it in a different way
in PHP, when session_start(); is called:
a random ID is generated by the server, e.g. jo96fme9ko0f85cdglb3hl6ah6
a file is saved on the server, containing the data: e.g. /var/lib/php5/sess_jo96fme9ko0f85cdglb3hl6ah6
the session ID is sent to the client in the HTTP response headers, using the traditional cookie mechanism detailed above: Set-Cookie: PHPSESSID=jo96fme9ko0f85cdglb3hl6ah6; path=/:
(it can also be be sent via the URL instead of cookie but not the default behaviour)
you can see the session ID on client-side with document.cookie:
the PHPSESSID cookie is set with no expiration date, thus it will expire when the browser is closed. Thus "sessions" are not valid anymore when the browser is closed / reopened.
can be set/read in PHP with $_SESSION
the client-side does not see the session data but only the ID: do this in index.php:
<?php
session_start();
$_SESSION["abc"]="def";
?>
The only thing that is seen on client-side is (as mentioned above) the session ID:
because of this, session is useful to store data that you don't want to be seen or modified by the client
you can totally avoid using sessions if you want to use your own database + IDs and send an ID/token to the client with a traditional Cookie
A session is a chunk of data maintained at the server that maintains state between HTTP requests. HTTP is fundamentally a stateless protocol; sessions are used to give it statefulness.
A cookie is a snippet of data sent to and returned from clients. Cookies are often used to facilitate sessions since it tells the server which client handled which session. There are other ways to do this (query string magic etc) but cookies are likely most common for this.
Cookies are stored in browser as a text file format.It stores limited amount of data, up to 4kb[4096bytes].A single Cookie can not hold multiple values but yes we can have more than one cookie.
Cookies are easily accessible so they are less secure. The setcookie() function must appear BEFORE the tag.
Sessions are stored in server side.There is no such storage limit on session .Sessions can hold multiple variables.Since they are not easily accessible hence are more secure than cookies.
One part missing in all these explanations is how are Cookies and Session linked- By SessionID cookie. Cookie goes back and forth between client and server - the server links the user (and its session) by session ID portion of the cookie.
You can send SessionID via url also (not the best best practice) - in case cookies are disabled by client.
Did I get this right?
Session
Session is used for maintaining a dialogue between server and user.
It is more secure because it is stored on the server, we cannot easily access it.
It embeds cookies on the user computer. It stores unlimited data.
Cookies
Cookies are stored on the local computer. Basically, it maintains user identification, meaning it tracks visitors record. It is less secure than session.
It stores limited amount of data, and is maintained for a limited time.
Related
I have a weird problem. I have a web page, that on the main page sets a session variable for each user that visits, and then on the next pages if the session variable is set, some stuff is shown, and some other isn't. The variable i'm setting is just an "1".
$_SESSION['user_id'] = $user_id;
Everything is simple, everything is working great, but I have this one user, that the server doesn't save the session variable for. Just one guy as far as I know. What can be causing this behaviour? He is using a mac if that matters, but on other macs the website works great.
Thanks.
When you call session_start() PHP sets a cookie with just the PHPSESSID variable set. This variable is used to identify the client browser with the session data on the server. If your user has disabled cookies, then it is not possible to use sessions without passing PHPSESSID back and forth in every request via GET or POST.
HTTP is a stateless protocol. IF session would be only in server side, how could it be able to distinguish between users?
[HTTP is a stateless protocol means: HTTP requests are responded from the server, and it forgets who sent the request, where did that come from.]
This is why cookies are storing the session ids.
In other words, if a user is disabling the cookies, he is not allowing PHP to set the session for himself. This is the reason behind.
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PHP session or cookie
We are developing a new project where we want to keep track of some information regarding the user from page to page, in terms of security, reliability and server usage is it better to do so with sessions or with cookies? What are the ups and downs of using one method or another.
For example to keep track if the user has successfully logged in or not, or to keep track of the language that the user selected.
Basically we want to know how to decide if we should use cookies or sessions, obviously if we want to keep track of data occurring within different visits to the page in different occasions and even different days the answer would be to use a cookie, but what about keeping track within the navigation of the page without closing the browser.
Thanks
A cookie is a small piece of text that is sent by the server to the client in the HTTP response headers. The client will store it locally and return it back to the server with every request in the request headers. That allows the implementation of some state in the otherwise stateless HTTP protocol.
A session is a concept typically implemented on top of cookies. The server sends a meaningless, unique session token (a random id) as a cookie to the client and the client returns it on every request. Server-side this id is associated with some data. Every time a client sends its session token back to the server in a request, the server looks up the data associated with that token.
The transfer of the session id back and forth between the client and the server can also happen by embedding the session id into all URLs or form requests, it doesn't have to be cookies. Embedding session ids in the URL is a bad idea though, since that allows accidental session transfers if URLs are shared between different users (see below). These days sessions are typically implemented using cookies client-side.
Conceptually cookies and sessions are extremely similar, they both implement state in HTTP. The difference is that a cookie can only store a small amount of data which is transferred back and forth on every request and is editable by the user (because it's information stored on the client); while a session stores all data server-side and is thereby only limited by the server's resources. The only vulnerability sessions have is that if a user can guess or steal the session id of another user, he can impersonate that user. That's known as session hijacking. Plain cookies have no security whatsoever and should not be used for anything important (as in, the user can see and edit the contents, so storing userloggedin=yes in a cookie is the worst thing you can do).
Hi I would like to know the difference between a php session and a cookie
The main difference being that session data is stored on the server, while cookie data is stored on the client. Therefore, a client can easily modify the cookie contents, but will have to work way harder to modify the session contents.
Cookies are a means to store information in the end-user's browser, so that the server can track the end-user.
Sessions are also implemented by using cookies, but the actual data is not in the browser; rather, it is stored in the user's session record on the server. In the case of sessions, cookies are used to identify a particular end-user's session identifier on the server records. Hence, they are a more secure way of storing user information.
A cookie is a ~piece of data stored on the client side.
Data stored in session is stored on the server side, and the various sessions are identified by cookies.
There are session and Cookies, both are used to store values or data. But there are some key differences between session and cookie: a cookie stores the data in your browser and a session is stored on the server. Cookie data is available in your browser up to expiration date and session data available for the browser run, after closing the browser we will lose the session information.
A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user's computer. Each time the same computer requests a page with a browser, it will send the cookie too.
A session variable is used to store information about, or change settings for a user session. Session variables hold information about one single user, and are available to all pages in one application.
A cookie is an unique information that the user sends to the web server with each request in order to identify him. This unique id could be used to store information about this specific user on the server (session).
Cookies will only expire on expiry time or if you explicitly clean cookie / cache of your browser. Cookies will retain into the system even after you open your browser next day.
Cookies are stored on client's system so they are less secure.
Session will expire on its expiry time or if the browser has been closed. As session is stored on server so it is more secure.
So for a login module, a combination of session and cookie should be used
Cookies stored client side but session stored server side.
cookies is without sign out of the your email account and close it. once again can not enter username and password but your email account is open.
session is close the webpage once again open to starting page appier
best example to illustrate the difference bet. Session and Cookies is:-
when you Login as a member in any Site it Creates Sessions until you log out...
that is Session..
and Cookies when you browse websites the are stored on your computer's Main Memory that is Cookies
i-e Session is Server side
and cookies is Client side
We got three differences in general. The key difference would be cookies are stored in client side and sessions are stored in server side. The second difference would be cookies can only store strings. We can store our objects in sessions. Storing objects in sessions were really useful according to my experience. Another difference was that we could be save cookie for future reference, but session couldn’t. When users close their browser, they also lost the session.
PHP Sessions
PHP has built-in functions to save session variables. The variables are stored in state files. These state files need not be explicitly created and managed. The following are the steps for saving and retrieving values of session variables.
The setcookie() command must be issued before any printed output occurs because the cookie must be written as part of the HTTP header. PHP automatically parses any HTTP_COOKIE string into an associative array $_COOKIE. The value of the cookie can be retrieved from the cookie thus:
$_COOKIE["some_var"]
Cookie: A key/value pair that is stored by the user's browser and is available in the superglobal $_COOKIE array available in PHP. The cookie request is initiated with an explicitly defined expiration date. For example:
setcookie('cookieName', $some_value, time()+3600, "/", ".example.com")
On the next server request, $_COOKIE['cookieName'] will be available. If you use a browser tool to look at the cookie, it will have an expiration date.
Session Cookie: Identical to the above but defined without an expiration date. If you use the same browser tool it will say that the cookie expires at the end of the session; which is ultimately when you close your browser. For example:
setcookie('cookieName', $some_value);
PHP Session: a server side mechanism that will associate a bunch of data with a session id. Every time a session is invoked, it serializes/unserializes it. This could be more data than just a single key/value pair that a cookie supports, but the way of associating this data with a user is by creating a cookie (regular or session as described above) in their browser that contains the session id. This way, the right data can be retrieved for a given user based on the value of that cookie.
Both are super global, i.e, they can be used anywhere in the site.
Differences between sessions and cookies:
Cookies are stored in the browser (client side) while sessions are stored in the server (host).
Cookies are remembered till they are deleted while sessions are deleted when the user closes the tab/browser (depending on the browser).
Cookies can be seen by the user while sessions cannot.
Due to the reasons above, I would recommend to not store sensitive data in cookies and store the data that is to be remembered even after the user has left in cookies.
Cookie - Stored data in browser and will work on browser related and client side only...For example if you are trying to log in gmail account with username and password,After entered login successful if you close the current tab and after sometime opening same page the login page won't come it will open directly with login details..This is cookie..
Session - Stored data in server side for example same as cookie example after entered login details you will get notification as successful once you close the browser then open after some time it will ask again login details(more example shopping also)
What are sessions and cookies in php and where are they stored?
I searched but I can't find the exact answer.
HTTP is stateless. This means whenever you request something from a webserver, it will serve the requested page and forget you immediately.
Imagine a shopping cart:
You add something to the cart. The server will have some sort of data storage to remember that you put item X into the cart, but since HTTP is stateless, the next time you call the server, it won't remember it was you who put something into the cart. The webserver could create a form on the returned page and populate this with each and every item you added. Now you add another item, but also send, which item you already had added. Repeat. This is effectively transfering the entire state of your interaction on each and every request. But that's rather inefficient and insecure.
With Sessions enabled, the webserver will create a unique id, the so called Session ID for you. This will be used to link you and the cart on subsequent requests. Usually, the Session ID is sent to the browser in a Cookie. Technically, this happens through HTTP Headers:
Set-Cookie: PHP_SESS=abcdefg123456
The browser reads the headers and creates or updates the cookie file in the cookie storage inside the browser. Usually cookie files are nothing more but key/value stores in text files on your computer. If you want to have a look at them google for "where does [browsername] store my cookies".
On the next request to the same webserver, your browser will send the cookie along and the webserver is now able to associate this ID with some data store (whatever is set as the session save handler) on the server, for instance login information, the contents of a shopping cart, etc
See the reference to the PHP Manual I've linked below your question for further details.
Cookies are stored in the browser, not in PHP. You can get the cookies the browser sent by looking in $_COOKIE['cookiename'], but as far as i know you can't set cookies like that -- you need to use setCookie(), or possibly header('Set-cookie: ...').
The sessions can be stored anywhere, but they're most often just files on your server's filesystem; your php.ini (or the ini_get() function) would probably be helpful in finding out where. Try:
$session_file_name = ini_get('session.save_path')."/sess_".session_id();
A cookie is some piece of data the server requests the client to store and send in consequent requests.
A session is some data stored on the server, and connected to the user via a session id. This session id is most of the time stored in a cookie.
A session can be stored on the filesystem, most likely in a temp directory, but also in a database.
Both cookies and sessions have a expiration date connected to them, so they wont last forever.
Cookie is a small piece of data stored on the client-side(browser) and session is a text file stored on the server-side, whose name is stored in the cookie.
That's all.
I am interested in knowing how session management and cookies work in PHP. I want to know their underlying mechanism, like how the browser interacts with the cookies, and how the cookies are used to validate the session data in the server.
Is there any web resources that allow me to learn that?
In PHP in particular, the standard way sessions work is that PHP generates a random session ID, and puts it in a cookie. (By default called PHPSESSID) This cookie is handled by the browser by saving it locally on the user's machine, and is sent with every request to the domain it belongs to.
This session ID is then used to refer to a data store on the server machine, by standard located in /tmp/ on an apache install on linux. This is where everything in the $_SESSION array is stored between requests.
As you may notice, this is only as safe as the cookie is, as there is no real authentication between the user and server that the user is the "real" owner of the session ID. This means that so-called "session hijacking" is possible by sniffing the cookie and inserting the cookie with the session ID on the attacker's machine. This can be used to take over an account on a webpage, and browse around it just as if you were the original user, because to the server you are.
There's also an alternate, even more unsafe, way of keeping the session alive that PHP supports. This is done by sending the session ID as a GET variable with every link. As you may notice, this means that if a user simply copy-pastes one of these links, he will be giving away all his credentials. =)
Further information could be found in the PHP manual.
From PHP’s Session Handling manual:
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.
This unique id is a big random number that is stored on the server side to match it next time the client makes a new request. It typically goes into the /tmp directory.
A cookie is a bit of data that's associated with a HTTP address.
I.e.
1/ Browser requests www.google.com
2/ www.google.com response includes setting a cookie
3/ From this point on and as long as the cookie is valid (there's an expiry time associated with it), each subsequent request made by the browser to www.google.com/anything includes the cookie above
For details: http://en.wikipedia.org/wiki/HTTP_cookie
A cookie permits creating a session in the otherwise stateless HTTP protocol in the sense that it allows a client-server conversation to be isolated from other clients interacting with the server.