<?php

$request = "cmd=_notify-validate";
foreach ($_POST as $varname => $varvalue){
    $email .= "$varname: $varvalue\n";
    if(function_exists('get_magic_quotes_gpc') and get_magic_quotes_gpc()){
        $varvalue = urlencode(stripslashes($varvalue));
    }
    else {
        $value = urlencode($value);
    }
    $request .= "&$varname=$varvalue";
}
$ch = curl_init();
curl_setopt($ch,CURLOPT_URL,"https://www.sandbox.paypal.com/cgi-bin/webscr");
//curl_setopt($ch,CURLOPT_URL,"https://www.paypal.com");
curl_setopt($ch,CURLOPT_POST,true);
curl_setopt($ch,CURLOPT_POSTFIELDS,$request);
curl_setopt($ch,CURLOPT_FOLLOWLOCATION,false);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
$result = curl_exec($ch);
curl_close($ch);
switch($result){
    case "VERIFIED":
        // verified payment
        break;
    case "INVALID":
        // invalid/fake payment
        break;
    default:
        // any other case (such as no response, connection timeout...)
}