PHP refresh, how can I stop the previous function being called again on page refresh?

Question

I have a function that imports a files contents into mySQL and returns the results. If i refresh the page and click "yes" it will do it again doubling the output with the same content.

How can I stop this happening? In this particular case there is no URI in the address bar but on other functions there is.

Have your script check whether that record is already in the database? — Oliver Charlesworth, Apr 17 '11 at 15:53
Could do, but the only way to check is on the filename, and if the filename already exists it renames it and adds it anyway. — Nicekiwi, Apr 17 '11 at 15:54

score 2 · Accepted Answer · answered Apr 17 '11 at 15:54

2

You should just check if the contents in the database exist, if they don't, fill them. Otherwise don't run the function.

psuedo-code:

if !database.containsRecords
  fillDatabase()
end

On top of this, it is always good practice to redirect after a POST request. So you would want:

fillDatabase();
header("Location page.php");
exit();

answered Apr 17 '11 at 15:54

Mike Lewis

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Can i pass a success msg along with that? – Nicekiwi Apr 17 '11 at 16:17
@Ezra: Have the destination page say "success". – Oliver Charlesworth Apr 17 '11 at 16:19
Not quite the most dynamic of processes. – Nicekiwi Apr 17 '11 at 16:21
@Ezera, yes. Just store the message in a session variable. Look up http://php.net/manual/en/ref.session.php – Mike Lewis Apr 17 '11 at 16:23
I might just ask, after the session variable has been displayed and you refresh the old msg will still be there. Getting a lil picky here, but is there a way to make the msg only display once? – Nicekiwi Apr 17 '11 at 16:45
Nvm, calling $_SESSION['msg'] = ''; below where-eva I declared it did the trick. =) – Nicekiwi Apr 17 '11 at 16:50

score 1 · Answer 2 · answered Apr 17 '11 at 15:53

1

Query the database on each page load and see if it has already been populated. If it has been populated then don't attempt to populate it again.

answered Apr 17 '11 at 15:53

Treffynnon

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score 1 · Answer 3 · answered Apr 17 '11 at 15:54

1

You should use the POST-redirect-GET pattern.

After updating the database, send an HTTP redirect to a separate page that displays the results.
Refreshing the browser will reload that separate page.

answered Apr 17 '11 at 15:54

SLaks

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And using the browser back button will mess up anyway. Yes some modern browsers prevent resending POST data but not all. – Oliver A. Apr 17 '11 at 15:58
Yup you really should do a redirect on success. Actually you should do this for all forms. It is best practise. – PeeHaa Apr 17 '11 at 16:00
@Oliver: Wrong. Redirects do not create separate entries in history; going back will go back to the page that submitted the form. – SLaks Apr 17 '11 at 16:03
Yes if you do it right. Some redirects DO create entities and sometimes bad redirects even trap you on a page. – Oliver A. Apr 17 '11 at 16:11
@Oliver: Javascript redirects (`location.href = ...`) can cause history entries, and HTML meta-refresh bounces could (not sure on that one). HTTP 30x redirects generally don't (except on exceptionally poorly-written browsers, none of which are in common use). – cHao Apr 17 '11 at 16:17

score 0 · Answer 4 · answered Apr 17 '11 at 16:08

I assume you use a POST form to upload the file. You can include a hidden input field with an pseudo random unique id in your form. If the user resends the data via POST you can check if you already processed this request. Hidden fields are not save because a user might edit them, but you can detect accidental resubmits.

PHP refresh, how can I stop the previous function being called again on page refresh?

4 Answers4