Nested if conditions issue - php

Question

I have this part of code which i use in order to prevent query submission twice! Now, this is the query i use in order to make it work, and it works.
$form_secret = isset($_POST["form_secret"])?$_POST["form_secret"]:'';
$query = "INSERT INTO coupon (user_id,points) VALUES ('$user_id','$points')";
$result=mysql_query($query);
if ($points == 250)
{
$url="http://testext.i-movo.com/api/receivesms.aspx?".$str_from.$str_zip.$phone.$str_time.$date1.$str_msg;
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$output = curl_exec($ch);
curl_close($ch);
return $output;
}
else if ($points == 500)
{
$url="http://testext.i-movo.com/api/receivesms.aspx?".$str_from.$str_zip.$phone.$str_time.$date1.$str_msg;
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$output = curl_exec($ch);
curl_close($ch);
return $output;
}
else
{
echo "We are sorry, you don't possess enough points in order to take the coupon";
}
Perfect up to now!
What i need then is to prevent double submission and hence i'm using this code here, but the problem is, when i put all the above code inside this one, it doesn't work.. anyone please tell me how to unite this two codes? Thanks..
if(isset($_SESSION["FORM_SECRET"]))
{
if(strcasecmp($form_secret, $_SESSION["FORM_SECRET"]) === 0)
{
/*Put your form submission code here after processing the form data, unset the secret key from the session*/
unset($_SESSION["FORM_SECRET"]);
}
else
{
//Invalid secret key
}
}
else
{
//Secret key missing
echo "Form data has already been processed!";
}

Answer 1

$_SESSION["FORM_SECRET"] will not be set by default, so you can never submit the form in the first place.
Reverse the process. Give the form a secret key, and store that secret in the session when the form is submitted. Then, on the next submit, you can check if $_SESSION["FORM_SECRET"] is set (and is the same as the submitted secret), so you'll know that it's the second submit of the same form.