'Back' problem

[vanjito]

I have a form that validates data and if all is ok then inserts some in mySql

Now, I'm concerned about 'Back' action... when a user clicks last submit button, all data is succesfully validated and inserted in database, and then, if he clicks 'Back' and submit agan, my script will insert the data in database once more... 🙁

How can I prevent this?

[Frederick]

You can setup a time limitation for submission during original submission by adding a field to hold the submission time. This will check if he/she has submitted anything within the last 2 minutes and block them till they have elapsed the waiting period.

$posttime = time()-120;
$sql = mysql_query("SELECT * FROM table WHERE userid='$userid' AND posttime > $posttime") or die (mysql_error());
if (mysql_num_rows($sql)) {
    // Already posted
} else {
    $originalposttime = time();
    // SQL INSERT Query
}