you can find a similar question here PHP Post Request inside a POST Request but this is not working in my context.
I have a form (reservation form for a tour website) an
You can't. HTTP makes no provisions for redirecting with anything in the request body (which is where POST data goes). You can only redirect with a GET request. So the typical way to do this is to take the user to a second page that has a button to "Continue to PayPal", or something of that nature. That button POSTs all the data to PayPal as normal.
For what it's worth, if this is for the PayPal "Buy Now" button, they actually (even if not documented) allow sending all those form variables in the GET request, via the URL. We do this in one of our applications where we "track" the start of the payment process and then redirect to a PayPal URL containing all the form fields as a query string, then "complete" the transaction as the user returns.
To create a POST request, open a up a TCP connection to the host using fsockopen(), then use fwrite() on the handler returned from fsockopen() with the same values you used in the header functions in the OP. Alternatively, you can use cURL.
<?php
if(isset($_POST['Name'])) $Name = $_POST['Name'];
if(isset($_POST['Email'])) $Email = $_POST['Email'];
if(isset($_POST['Message'])) $Message= htmlentities($_POST['Message']);
$Curl_Session = curl_init('http://www.yoururl.com/script.php');
curl_setopt ($Curl_Session, CURLOPT_POST, 1);
curl_setopt ($Curl_Session, CURLOPT_POSTFIELDS, "Name=$Name&Email=$Email&Message=$Message");
curl_setopt ($Curl_Session, CURLOPT_FOLLOWLOCATION, 1);
curl_exec ($Curl_Session);
curl_close ($Curl_Session);
?>
Where $Message would be your variables.
EDIT: i answered this long ago maybe i did forget to reference from php.net but here is the link per comment http://www.askapache.com/htaccess/sending-post-form-data-with-php-curl.html as Reference
Well, I suppose that if you are talking about keeping data in your own website between pages you need to use PHP's session functions
To start the session just do session_start();
and to add session vars just use the superglobal array $_SESSION['myvar'] = $value;
you can then read them through the same means print_r($_SESSION[]);
However if you are talking about sensing data with the paypal API I highly recommend looking at their developer API manual.
Hope that helps, RayQuang