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.
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 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 have a PHP application where users can apply for a bonus. But there is a confirmation page before the bonus redemption code runs.
The issue is that in IE, if you hit f5 right after you click the continue button, the confirmation page refreshes while the bonus redemption code had already been triggered by the continue button and actually goes through. But because the user still sees the confirmation page, they would hit the continue button again and now they get an error cause they are already registered.
Is there a way i can disable the f5 button using javascript? Is this the best way to go about this? I have tried many scripts i found online to do this, but none of them achieves it. Is there a better way I can go about this? Perhaps from the application side?
Edit: If the outcome of claiming a bonus is databased, you can load existing claims on your confirmation screen and test that one already exists.
Edit: the other neat trick you can do is serailize/json_encode the $_POST and produce a hash from this, store it in the database or user session, and test against it.
I would generate and database a single use token (hash) for the form as a hidden field, if post data is re-sumbited, the token would have already been consumed, and you can invalidate the post request.
There are couple of methods to solve your issue:
Checkout here: http://bjw.co.nz/developer/general/75-how-to-prevent-form-resubmission
I have been using second method (Using sessions) and it's really working well.
I have a html file that has two buttons, approve and reject. I want that if someone clicks on the approve button, I want the box to disappear and display a message PERMANENTLY.
By permanently I mean that it should not return the box when I refresh the page.
Is it possible with JS or PHP or anything else?
Thanks.
Is it possible with JS or PHP or anything else?
Yes.
For a more detailed answer supply a more detailed question.
Uhm, presumably when someone clicks one of those buttons, you store a value somewhere indicating their action. You would normally check if the user has previously performed this action (or if it otherwise makes sense to display the buttons) and just not output them from your PHP script in that case.
Without more details about your code it'll be impossible to provide any more help than this.
You either need to store a cookie that you can check if they clicked or you need to store a list of IP's and what they clicked. That's the hard part
Hiding and displaying the box is as easy as using jquery and the onclick element in html.
Edit:
I agree with the above answer without more details it is hard to provide a working solution.
js will not be able to do something like this by itself. you need some sort of back end server processing or a cookie that will detect the user when they go to the page and then save their button click in a server side db or client side cookie... then when the user comes back it checks the back end data source or the client side cookie and makes the changes either client side with js or server side with php
I expect you'll need to set a cookie when you put up the message. That's only permanent as long as they keep the cookie, though. For real permanence you'll need to associate the message state with their login/customer info and retrieve that every time they come back to the site. Which means you'll have to force a login before they get to the form.
The problem with trying to do something dynamic, then make it permanent, but only for that user, is that you have to get over the statelessness of the web. You have no idea who you're dealing with from one visit to the next. To get over that, you either need to tag them (by setting a cookie) so you'll recognize them on their next visit, or you need to make them identify themselves (by forcing a login).
I have an application that supplies long list of parameters to a web page, so I have to use POST instead of GET. The problem is that when page gets displayed and user clicks the Back button, Firefox shows up a warning:
To display this page, Firefox must send information that will repeat any action (such as a search or order confirmation) that was performed earlier.
Since application is built in such way that going Back is a quite common operation, this is really annoying to end users.
Basically, I would like to do it the way this page does:
http://www.pikanya.net/testcache/
Enter something, submit, and click Back button. No warning, it just goes back.
Googling I found out that this might be a bug in Firefox 3, but I'd like to somehow get this behavior even after they "fix" it.
I guess it could be doable with some HTTP headers, but which exactly?
See my golden rule of web programming here:
Stop data inserting into a database twice
It says: “Never ever respond with a body to a POST-request. Always do the work, and then respond with a Location: header to redirect to the updated page so that browser requests it with GET”
If browser ever asks user about re-POST, your web app is broken. User should not ever see this question.
One way round it is to redirect the POST to a page which redirects to a GET - see Post/Redirect/Get on wikipedia.
Say your POST is 4K of form data. Presumably your server does something with that data rather than just displaying it once and throwing it away, such as saving it in a database. Keep doing that, or if it's a huge search form create a temporary copy of it in a database that gets purged after a few days or on a LRU basis when a space limit is used. Now create a representation of the data which can be accessed using GET. If it's temporary, generate an ID for it and use that as the URL; if it's a permanent set of data it probably has an ID or something that can be used for the URL. At the worst case, an algorithm like tiny url uses can collapse a big URL to a much smaller one. Redirect the POST to GET the representation of the data.
As a historical note, this technique was established practice in 1995.
One way to avoid that warning/behavior is to do the POST via AJAX, then send the user to another page (or not) separately.
I have been using the Session variable to help in this situation. Here's the method I use that has been working great for me for years:
//If there's something in the POST, move it to the session and then redirect right back to where we are
if ($_POST) {
$_SESSION['POST']=$_POST;
redirect($_SERVER["REQUEST_URI"]);
}
//If there's something in the SESSION POST, move it back to the POST and clear the SESSION POST
if ($_SESSION['POST']) {
$_POST=$_SESSION['POST'];
unset($_SESSION['POST']);
}
Technically you don't even need to put it back into a variable called $_POST. But it helps me in keeping track of what data has come from where.
I have an application that supplies long list of parameters to a web page, so I have to use POST instead of GET. The problem is that when page gets displayed and user clicks the Back button, Firefox shows up a warning:
Your reasoning is wrong. If the request is without side effects, it should be GET. If it has side effects, it should be POST. The choice should not be based on the number of parameters you need to pass.
As another solution you may stop to use redirecting at all.
You may process and render the processing result at once with no POST confirmation alert. You should just manipulate the browser history object:
history.replaceState("", "", "/the/result/page")
See full or short answers