after searching (and testing) a way to offer a kind of go-back button I am asking that question here (maybe there is an easy solution).
I have a description about orienteering on my website (5 pages): http://www.uhebeisen.net/o-def/o-definition_ge.php
There are many websites from abroad having a link to this pages. Now I'd like to get their URL if a websurfer is entering my pages. Then I can place a button go-back to my navigation list that brings him back to his page from where he clicked the link to my description-pages.
I've seen solutions using javascript:history.go(-1) or $_SERVER['HTTP_REFERER'] with PHP but problem is that a websurfer can move around my pages and if finishing his reading from any page should be provided with his (calling) URL, e.g. the one of his University.
So I need to catch his URL and store it in a safe place until he decides to leave. And if he returns to the starting page while surfing on my pages his URL shouldn't be overwritten.
Since I do not program - just copy&paste and try to understand what happens. Any suggestion on how this can be done is welcome.
thank you George, that one worked
I wasn't aware to place the session_start at the very beginning of the file that's why I get the two warnings.
While testing this function I found that the session variables were not always cleared by the browser. Especially with Firefox, it keeps the calling URL almost forever (WinXP, FF 5.x) whereas Firefox 5 on the Mac, Safari (Mac) and Camino (Mac) work as expected: after restarting the program I can test successfully with another website.
Does Firefox have different setting possibilities in regard of sessions than other browsers?
You should store $_SERVER['HTTP_REFERER'] in the user's session upon arrival. Using this method, the value won't be overritten when the user browses within your site.
session_start();
if ( !isset( $_SESSION['referrer'] ) ) {
if ( !empty( $_SERVER['HTTP_REFERER'] ) ) { // Because not all browsers set this
$_SESSION['referrer'] = $_SERVER['HTTP_REFERER'];
}
}
One way to do it would be to store somewhere (perhaps in a cookie or session, which easy to do with your PHP page) the page they're coming from, but only if that page is not on your website's domain. This would require some if-statements to set the cookie/session value appropriately, but it can be done relatively easily using particular parts of the referrer variable. There is probably a more efficient way to store this, but this is one that jumps to mind right away.
EDIT: I highly recommend George's solution, much better way to do this.
Have you tried using a session?
session_start();
if( !isset($_SESSION['refer']) )
{
$_SESSION['refer'] = $_SERVER['HTTP_REFERER'];
}
then, once your ready to make the button, set the link to $_SESSION['refer'].
In my past projects I usually stores the redirect url following this process:
search for a query string parameter url (www.yoursite.com/?redirect_url=my_encoded_url)
If search at point 1 doesn't return any results, then I checks for the HTTP_REFERER
In both cases, I stores that value in a SESSION variable after verified that the url belongs to my site's domain.
Related
I am working on a my site to allow users to take test so they can see how much they know of a particular subject. I am running into a little problem though. Once a user submits the test for grading, how do I prevent them from going back to the test page? I am on a Mac with Safari running and when I click the back button in my web browser after I submit the test it leaves all of the answers I answered filled out. I want it do this: When a user submits a test and they click the back button in their web browser it redirects them to the main test page.
I am using PHP and MYSQL. I even have the test pages setup so that the user must come from a certain url (I am using HTTP_REFERER) and I have tried other stuff such as sessions but I cannot seem to figure this out. Any help is greatly appreciated.
You don't stop them.
Instead change your application so that it still works even if they go back. You can embed a unique number in a hidden field on the page and if they resubmit the same test twice you can detect it and display an appropriate error message. You should also think about what should happen if they modify the unique number.
If you don't want people to post different answers once they have already answered, all you have to do is check, in the script that accepts the test for grading, that the user has never submitted the test before. If you don't, a clever student will always be able to to circumvent your protection by sending an appropriate request directly to that script.
If you don't want people to see previous answers (for instance, if you have two people grade their tests on the same computer), consider using AJAX on the test page to submit the answers and then erase them from the fields. This way, most browsers will not remember the answers and the back button will not un-erase data that was erased by JavaScript.
At the top of the grade page, put the following:
session_start();
$_SESSION['testcomplete'] = 'yes';
Then at the top of each page of the test, put this:
session_start()
if ($_SESSION['testcomplete'] == 'yes') {
header("Location:cheater.php");
}
You could simulate there being no page to go back to. From one page, generate each test page using jQuery, and provide no way to go back, only forward. The back button would take them to the page before they ever launched the test, and you could allow them to launch the test again and generate the right part where they should be. This would be pretty easy, if you haven't gone too far in development the current way.
You could run javascript that clears out all the answers. You might also just allow one submission so that subsequent submissions don't get processed. HTTP_REFERER is usually sent, but can be spoofed and forged by an altered browser.
On the top of the script POST-ing the answers, do a check whether you have the test results in the database for the current user for this test. If you do, redirect to results.
if(get_test_results($user)){
$test_url = get_test_url($user);
header( "Location: $test_url" ) ;
}
Disabling the back button is not a good idea.
I was facing a similar problem making an online examination myself
what I did is
I provided a session variable such that if the user pastes the previous page's URL in the address bar then on loading the page the page is automatically forwards to the next desired page. Whether the page whose URL was mentioned is the being visited the first time or being revisited is determined by the value of the session variable
If the user instead of loading the page does a go back via the browser button the it automatically redirects to the next page in history as :
javascript:window.history.forward(1);
Hope this helps :)
http://www.htmlgoodies.com/tutorials/buttons/article.php/3478911/Disabling-the-Back-Button.htm you should be able to do it in javascript.
I don't know is there is a PHP function like the ones that start with $_SERVER['']
That tell user which page he came from, on his current page.
ex. If I was browsing foo.com?id=abc then went to foo.com?id=efg, I need the current page to tell me that I came directly from foo.com?id=abc
I need this code badly, so any help is appreciated.
It is $_SERVER['HTTP_REFERER']. But it is filled only if browser did so. Otherwise you need to track user yourself (i.e. by storing last page in session)
The $_SERVER variables should not be relied upon to provide accurate answers. You should use PHP Sessions to track what page they come from, and simply update it everytime they go to a new page. Something along the lines of:
session_start();
if(!empty($_SESSION['visited_pages'])) {
$_SESSION['visited_pages']['prev'] = $_SESSION['visited_pages']['current'];
}else {
$_SESSION['visited_pages']['prev'] = 'No previous page';
}
$_SESSION['visited_pages']['current'] = $_SERVER['REQUEST_URI'];
Then to access the previous page, access the: $_SESSION['visited_pages']['prev']
The HTTP_REFERRER gives address of the page that requested the file. For example an image on a page is a separate request, and this request has a $_SERVER['HTTP_REFERRER'] set to the page.
I don't think browsers allow servers to access history. It can be done with JavaScript, though only a back button can be provided, the url cannot be accessed easily. Though it can be achieved using a simple css and javascript trick by accessing the computed color to a link.
Yes, and this is not only in PHP, this is a part of the HTTP protocol specification, Use:
$_SERVER['HTTP_REFERRER']
I have been looking for ever for a solution to my problem - I’m not a PHP newbie but am not overly experienced in it.
My problem is this:
I have a set of sites - one being the parent site. I want to have it so that if I hit any of my child sites from the parent site only, a back to parent button appears (wrapped in a div). If I hit any of the child sites directly or from another referrer then the button doesn't appear.
I have this working using HTTP_REFERER but I would like the button to remain visible when you click the through the site (obviously the referrer changes once I start clicking through the site).
This works for the button appearing on first hitting the site:
<?php if (preg_match("~^http://www.mysite.com~i", $_SERVER['HTTP_REFERER'])) { ?>
<div>Back</div>
<?php } ?>
But as I say I would like it to remain whilst I am navigating the site - I have looked at setting up a session but I can't get this to work either - the referrer always changes once I start navigating.
I appreciate this is a little vague but I have tried so many code samples and they all seem to have the same issues.
Any help would be much appreciated.
Thanks
Well the HTTP_REFERRER is indeed the last referer of the current page, so you have to store and start a session the first time you enter the site.
Sessions are usually a very simple subject that should work out of the box:
session_start();
session_regenerate_id();
if (preg_match("~^http://www.mysite.com~i", $_SERVER['HTTP_REFERER'])) {
$_SESSION['parentsite'] = true;
}
And later in your code do:
<?php if(isset($_SESSION['parentsite']) && $_SESSION['parentsite'] == true){ ?>
<div>Back</div>
<?php } ?>
Now if your sessions still don't work with that, it could be a COOKIE problem or a server configuration problem...
<?php
session_start();
if (!isset($_SESSION["ref"])){
$_SESSION["ref"] = $_SERVER["HTTP_REFERER"]; //record first instance
} else if (isset($_SERVER["HTTP_REFERER"])){
$ref = $_SERVER["HTTP_REFERER"];
if ($ref != $_SESSION["ref"]){
$_SESSION["ref"] = $ref; // record new ref
}
}
if ($ref = $_SESSION["ref"]){
echo "Back
}
BUT I agree with Pekka, that you should use custom site_id which is passed along whilst you navigate your site. Relaying on HTTP_REFERER is generally unsafe. And using session would run you into problem if you come to your master site from two child sites, as session would hold only latest ref.
In other solution of ours, we use get param "current_ref", which contains encoded referer url, created by the source site. This param is "sticky", and is passed all along the way, so at any point of time you can return to the originating site. Probably it would be better for you to implement such approach as well.
Edit: On closer look, a session based approach might be just enough for this specific situation, if there is only one parent site and multiple children, but no multiple parents! In a more complex situation however, sessions will send you to hell, so I'll leave this answer in place.
This is not trivial -
you could use sessions to store the referrer target across pages, but that would get confused if the user opens multiple instances of the same page from different referrers, which is horrible for usability
or send a unique key along with each request that points to the correct "back" target. (It could also be the base64 or URL encoded URL itself, but that would make the URLs look long and ugly...)
The latter is a very clean approach, but a pain to implement consistently.
One other (crazy and untested) idea that comes to mind is storing a base64 encoded representation of the referrer URL using JavaScript in the window.name property. The nice thing about that is that unlike a cookie, it stores the "back" target for the current window only. I can't guarantee this will work, but it might be worth following up on if you really want to do this.
As soon as I saw your question I thought that a SESSION would be the key.
You could set a session cookie and then test to see if the cookie already exists.
session_start();
if (preg_match("~^http://www.mysite.com~i", $_SERVER['HTTP_REFERER']) ||
isset($_SESSION['show_back_button']))
{
// Set the session value
$_SESSION['show_back_button'] = true;
echo '<div>Back</div>';
}
I am working on a my site to allow users to take test so they can see how much they know of a particular subject. I am running into a little problem though. Once a user submits the test for grading, how do I prevent them from going back to the test page? I am on a Mac with Safari running and when I click the back button in my web browser after I submit the test it leaves all of the answers I answered filled out. I want it do this: When a user submits a test and they click the back button in their web browser it redirects them to the main test page.
I am using PHP and MYSQL. I even have the test pages setup so that the user must come from a certain url (I am using HTTP_REFERER) and I have tried other stuff such as sessions but I cannot seem to figure this out. Any help is greatly appreciated.
You don't stop them.
Instead change your application so that it still works even if they go back. You can embed a unique number in a hidden field on the page and if they resubmit the same test twice you can detect it and display an appropriate error message. You should also think about what should happen if they modify the unique number.
If you don't want people to post different answers once they have already answered, all you have to do is check, in the script that accepts the test for grading, that the user has never submitted the test before. If you don't, a clever student will always be able to to circumvent your protection by sending an appropriate request directly to that script.
If you don't want people to see previous answers (for instance, if you have two people grade their tests on the same computer), consider using AJAX on the test page to submit the answers and then erase them from the fields. This way, most browsers will not remember the answers and the back button will not un-erase data that was erased by JavaScript.
At the top of the grade page, put the following:
session_start();
$_SESSION['testcomplete'] = 'yes';
Then at the top of each page of the test, put this:
session_start()
if ($_SESSION['testcomplete'] == 'yes') {
header("Location:cheater.php");
}
You could simulate there being no page to go back to. From one page, generate each test page using jQuery, and provide no way to go back, only forward. The back button would take them to the page before they ever launched the test, and you could allow them to launch the test again and generate the right part where they should be. This would be pretty easy, if you haven't gone too far in development the current way.
You could run javascript that clears out all the answers. You might also just allow one submission so that subsequent submissions don't get processed. HTTP_REFERER is usually sent, but can be spoofed and forged by an altered browser.
On the top of the script POST-ing the answers, do a check whether you have the test results in the database for the current user for this test. If you do, redirect to results.
if(get_test_results($user)){
$test_url = get_test_url($user);
header( "Location: $test_url" ) ;
}
Disabling the back button is not a good idea.
I was facing a similar problem making an online examination myself
what I did is
I provided a session variable such that if the user pastes the previous page's URL in the address bar then on loading the page the page is automatically forwards to the next desired page. Whether the page whose URL was mentioned is the being visited the first time or being revisited is determined by the value of the session variable
If the user instead of loading the page does a go back via the browser button the it automatically redirects to the next page in history as :
javascript:window.history.forward(1);
Hope this helps :)
http://www.htmlgoodies.com/tutorials/buttons/article.php/3478911/Disabling-the-Back-Button.htm you should be able to do it in javascript.
Ok, firstly this is not about forms this is about consistent layout as a user explores a site.
let me explain:
If we imagine a (non-ajax) digital camera online store, say someone was on the DSLR section and specified to view the cameras in Gallery mode and order by price. They then click onto the Compact camera's page. It would be in the users interests if the 'views' they selected we're carried over to this new page.
Now, i'd say use a session - am i wrong?
are there performance issues i should be aware of for a few small session vars ( ie view=1 , orderby=price) ?
Speaking of performances, there should not be much problems with either solutions.
Some things that have to be considered are :
With GET, if an URL gets copy-pasted (in a email or MSN), the other who will receive the URL will have the same GET parameters
is that a good thing, or not ?
On the other hand, session will not be shared, if an URL is copy-pasted
which means the first guy will say to the other "key, look at this", and the second guy will not see the same page ;; same thing with bookmarking, should I add.
GET is specific to each URL
While SESSION is shared accross all tabs of the user
Which means browsing with several tabs at the same time can cause troubles, when using Session, if you don't take care of that
I'd say use both. Store it in the session, but also put it in the get parameters for the page.
Why? This way the user is able to carry his options from page to page, but they are also in the URL so if he sends search results to his friend, his friend sees them the exact same way he did.
No, the session's performance will not degrade by putting those small variables in there. Unless you're storing monolithic arrays in your session, the vast majority of the time loading a session will be reading it from its storage medium (file, database, memcache, etc).
You should use GET in your case.
There is one simple rule in the web development: each page with different content must have it's own address. So, customer can save any page into favorites, send it to a frend. It's pain in the bottom then someone sends you a link to a particular page saying "Look!" but site uses frames and you land at the front page and dunno where to look.
You can save user's preferences into his profile/cookie (not session), but it should be reflected in the address bar as well.
Sessions being used for completely different purpose, shopping cart is an example.
It's a subjective question, it would work either way.
Personally I would go with sessions as it doesn't interfere with the URL so people can bookmark the url if they wanted.
However the argument for that would be if they bookmarked it they might see different things if it was done using $_SESSION.