page refreshing allows duplicates to be inserted again and again

[siddu05]

I have a form with some user details like first name , last name, email and posting them to the second page , here my database code runs and insertion done , , ,and redirection to signin.php , works fine , but after entering the firstform details it openini second form, , when i refresh the browser the insertion performed again, l how can i stop the resubmissoin of the page

[Rabbit]

Check for whether or not that row exists before inserting.

[Dormilich]

l how can i stop the resubmissoin of the page

set appropriate unique (composite) keys in the DB.

[koharu]

Both of the above are great ideas, and should be followed as a standard. You can also add header("Location: somewhere.php"); which will quickly redirect a person on successful completion of inserting into a Database, pressing the back button will take the person back to the form.
Another option is to use jQuery to post the data, and lock the form so no double clicking on buttons will cause issues.