Have two submit buttons with different values set to it. Then on the page that does the process act based on those values.
EX:
<input type="submit" name="confirm" value="Submit">
<input type="submit" name="confirm" value="Cancel">
on the next php page
if ($POST['confirm'] == "Submit")
{
// Add to database
}
else if ($POST['confirm'] == "Cancel")
{
// Don't Add to database
}