On my site, I have a form that users fill out to become a member. They fill out name, bday, email, etc. Then when they click submit, the data gets into mySQL. But sometimes when a user clicks submit many times or refreshes the page, the data gets inputted to the database more than once. How can I prevent this accidental submission? Is there a code I can use to only let one set of data get into the database?
This is also a problem in my comment section. I allow uses to put comments on people's profiles. But when they abuse the refresh button or submit button, I get like 10 of the same comments. I am trying to prevent users accidentally submitting a comment twice.
Thanks.
Create a UNIQUE constraint:
CREATE UNIQUE INDEX name_of_youw_index ON tablename(columnname);
INSERTs will now fail with double data.
In the first case you probably just want to add a unique index on the email address and use that to create a profile for that user.
In the second case, as I understand it, you are trying to prevent users from accidentally submitting data twice, not to completely prevent data being submitted twice. You probably don't want to prevent people from writing the same comment twice on the same page. If someone writes "Today was like yesterday!", you don't want to prevent them from coming back the next day and writing "Today was like yesterday!" again. This would be unnatural and the check could be expensive as it would require indexing a lot of data. I think you want to prevent someone from submitting the same form twice, regardless of whether the data is the same or not.
So the solution to your second example is to include a hidden field in your form that uniquely identifies it. When they submit the form, mark the value in the hidden field as used. If someone later submits a form with the same value in the hidden field, reject it.
Server-side: Implement throttling. Only allow 1 submission every 10 seconds or so.
Update: When you accept a form submission, record the timestamp you
made the submission in $_SESSION.
When you accept another (or rather,
every) form submission, check if the
value stored in $_SESSION is older
than 10 seconds. If it is, continue.
If it isn't, don't do any more work.
You could do it with just some
database stuff to I guess, but
$_SESSION is much simpler.
Client-side: Disable the submit button via Javascript when the form is submitted.
Make the email field in your database "unique", by adding a unique index to it.
If your database gets another entry with an email which has already been used then mysql throws an error - the error number is 1062.
If you wanted to then you could handle this error different from others.
mysql_errno()
http://www.php.net/manual/en/function.mysql-errno.php
In the case of the database duplicates, put a unique constraint on the field.
For both the database duplicates and the duplicate comments, disable the submit button for 2-3 seconds after it is pressed to prevent multiple submits.
Related
I'm trying to write an app that basically is a frontend for editing database records. I have heard that a way to ensure the right row in the DB is being updated is to include a hidden form field on the update form with the row unique ID in it, and use this to add a conditional to the backend update statement.
However, this seems insecure. Anybody could edit the HTML on the page pre-submit and change the record being updated, no? What is the proper way to pass the unique ID of the row the user is editing along with their edits? I would imagine this may be done with cookies/session tracking, but couldn't this be edited client side prior to submitting as well?
Thanks!
If a client is allowed to modify the record in question anyway, it doesn't matter whether he does so by modifying the id in a hidden field or by going to the correct page and submitting the form from there.
When any client submits any form, the server needs to a) make sure the client has the right to modify the record he attempts to modify and b) validate that the submitted data is allowable for the record. Then all your business rules are being protected and taken care of, whether the user uses the proper forms or not.
You can also save a hash of all hidden fields in the session server-side and check that on submission to catch hidden field-manipulation attempts, if that's still in your interest.
You may create a field with default value TIMESTAMP.
Also you may pass this data from one page to another using php sessions
More details here
Hope this helps.. :)
When you load the form page, store the id in the session however you want to.
When they submit, on the post page, grab the id from the session.
The insecure part is, how are you letting people decide which id they want to edit? Where is the input for that?
I have a form where a user submits data from various text fields on my webpage to mysql database. Is there any code I can use were it will not let them submit/update the data again? e.g it will redirect them to a page saying sorry wwe have already received your data.
I have a unique number for each user if this helps. any help is appreciated.
Use tokens, it will avoid double submits and CSRFs.
Simply add tokens to an array, $_session most likely, and pop them when used.
Also, disable the submit button with JS after a submit.
You can also set a var in the session user that says he already performed an action, exampled uploaded his picture. Unset it if there is an error in your upload script for instance.
When you receive the post, query the database for the unique user number. If you get back a non-empty result, then display the error. Otherwise, save the data to the database.
The biggest thing you need to determine is what your unique identifier will be. It sounds as though you already have one (you mentioned unique user number?) Your unique identifier could be an email address, or even the full set of submitted data.
There are other ways to emulate this, such as setting a cookie on the user's machine, or disabling the submit button, but, none of these are completely under your control. The user could easily get past them if they tried. Therefore, determining a unique identifier and validating server side is probably the best way to do it.
The answer hugely depends on the reason for which user might send the data twice.
in case of an accident, there is one technique, and all other won't help you even a bit.
in case of intentional duplication the technique is completely different and again there is no general solution - everything depends on the certain scenario.
If you care to explain your certain case, you will get a proper solution.
For the most silly case of pressing "Reload" on a page with post results, you have to redirect browser using Location: HTTP header, e.g.
header("Location: ".$_SERVER['REQUEST_URI']);
exit;
I've a php web page with a form. After filling the form in web page, I can submit it to the server. But after that, if I refresh the page, it inserts the same record to the database. Is there any solutions to this problem?
Use the POST/Redirect/GET pattern. This will prevent the user from being able to resubmit the same form.
There are a number of ways, for example:
Create a token which you insert into the form (hidden field). if the same token is submitted twice, discard the second submit.
Check in the database if an identical post already exists.
Save the form submit in a session variable.
Redirect the user to a second page after the submit, using the Post/Redirect/Get pattern (preferably in combination with one of the above).
Yep, do two queries. The first checks to make sure the data doesn't already exist in the DB, the second one does the insert if there is no duplicate data. There are a bunch of ways to go about checking to make sure the duplicate data doesn't exist, but this is the basic process you will want to go through.
Well, that's what Refresh means: "do it again."
You can check to see if data that matches the submitted data is already in the database. If so, you can reject the new submission.
Before inserting to the database check whether the same values are duplicates already, and if they are duplicates, don't insert. Checking for multiple columns helps even further. For example, instead of checking just for a "username", you would check for a "username" AND "password".
Obviously the examples above are fake, but you should get the point.
You can make a process.php page and set your form's action to it.
In process.php
//code to insert item to database
header('Location: YOUR_FORM_PAGE_HERE);
Then it will send them back to the original page and there won't be any post data
You could change your query to INSERT IGNORE INTO table_name ...
this will prevent you from inserting twice.
I'm currently developing a page where the user fills out a form, and when submitted they are taken to the next page. When on the next page, I want to have it so that if the user went back to the previous page using the back button, or hit refresh, the submission will not be saved into the DB.
Now I recall reading somewhere that if you had a way to make each submission unique, this issue is averted, but after screwing around for hours on end, for the life of me I cannot recall how this could be done (using PHP), so long story short has anyone ran into this, and if so, what was your solution?
Use the Post/Redirect/Get pattern to avoid this problem. See also Redirect After Post.
Another way is to generate an identifier using uniqid and include it in the form as a hidden input. On submission, store that identifier in a database column marked with a UNIQUE index. This will cause subsequent submissions to throw a SQL error, which your application can handle gracefully.
You can add any confirmation on the second page.
By adding any confirmation box or any button....
by which you can confirm that whether user want to save it or not....
and if you don't want any confirmation...then you can delete the last record....by using managing session...but it is not good practice to fire the query very soon and delete in that kind..
so best way will be by adding any confirmation msg....
I want to ask a best practice question.
Suppose I have a form in php with 3 fields say name, email and comment.
I submit the form via POST. In PHP I try and insert the date into the database.
Suppose the insertion fails.
I should now show the user an error and display the form filled in with the data he previously inserted so he can correct his error. Showing the form in it's initial state won't do.
So I display the form and the 3 fields are now filled in from PHP with echo or such. Now if I click refresh I get a message saying "Are you sure you want to resend information?".
OK.
Suppose after I insert the data I don't carry on but I redirect to the same page but with the necessary parameters in the query string. This makes the message go away but I have to carry 3 parameters in the query string.
So my question is:
How is it better to do this? I want to not carry around lots of parameters in the query string but also not get that error. How can this be done? Should I use cookies to store the form information.
Your first scenario seems the most valid.
i.e.
User submits the form
Some problem prevents submission, so form is re-displayed
If user "refreshes" they see the usual message about re-sending information (although their most likely path of progression is to re-submit the form that you are kindly re-populating for them).
The "Are you sure you want to resend information?" message is perfectly valid in the event of someone refreshing the page after a form submission, so don't write code to specifically break this behaviour.
I think generally people would temporarily store the submitted data in a session variable, and send the data back to the client.
Maybe it is besides the point but you mentioned "wrong dates", and I think many would say you should arrange things so that the user cannot unintentionally send you wrong dates.