why doesn't my paypal ipn work ?

[luke noob]

This script does not upload to the database, but it always says verified and pays ok through paypal. i have enabled ipn in sandbox, i think my payments.php page is wrong but not sure. I really dont know where to start, my connection to my database is correct and im using php 5

index.php....

<form id="contactForm" class="paypal" action="paypal/payments.php" method="post">
<input name="cmd" type="hidden" value="_xclick" />
 
                                                                                    <input name="no_note" type="hidden" value="1" />
 
                                                                                    <input name="lc" type="hidden" value="UK" />
 
                                                                                    <input name="currency_code" type="hidden" value="GBP" />
 
                                                                                    <input name="bn" type="hidden" value="PP-BuyNowBF:btn_buynow_LG.gif:NonHostedGuest" />
 
                                                                                    <input name="item_number" type="hidden" value="123456" />
 
                                                                                    <input type="submit"  value="Continue" />
 
                                                                                    <img style="padding-left: 10px; padding-top: 5px;" class="paypal_btn" alt="Pay with PayPal" 
                                                                                  src="http://bytes.com/images/payWithPaypal.jpg" title="">
 

payments.php.....

<?php
 
// Database variables
$host = "*****"; //database location
$user = "*****"; //database username
$pass = "*****"; //database password
$db_name = "*****"; //database name
 
 
 
// PayPal settings
$paypal_email = 'sandboxpaypalemail';
$return_url = 'http://www.mysite.info/i/payment-successful.php';
$cancel_url = 'http://www.mysite.info/i/payment-cancelled.html';
$notify_url = 'http://www.mysite.info/i/paypal/payments.php';
 
$item_name = 'Test Item';
 
// Payment Type
$PaymentType = $_POST['paymentAmount'];           
 
 
$item_amount = $PaymentType;
 
 
 
//Database Connection
$link = mysql_connect($host, $user, $pass);
mysql_select_db($db_name);
 
// Include Functions
include("functions.php");
 
 
 
           // Check if paypal request or response
if (!isset($_POST["txn_id"]) && !isset($_POST["txn_type"])){
 
    // Firstly Append paypal account to querystring
    $querystring .= "?business=".urlencode($paypal_email)."&";    
 
    // Append amount& currency (£) to quersytring so it cannot be edited in html
 
    //The item name and amount can be brought in dynamically by querying the $_POST['item_number'] variable.
    $querystring .= "item_name=".urlencode($item_name)."&";
    $querystring .= "amount=".urlencode($item_amount)."&";
 
    //loop for posted values and append to querystring
    foreach($_POST as $key => $value){
        $value = urlencode(stripslashes($value));
        $querystring .= "$key=$value&";
    }
 
    // Append paypal return addresses
    $querystring .= "return=".urlencode(stripslashes($return_url))."&";
    $querystring .= "cancel_return=".urlencode(stripslashes($cancel_url))."&";
    $querystring .= "notify_url=".urlencode($notify_url);
 
    // Append querystring with custom field
    //$querystring .= "&custom=".USERID;
 
    // Redirect to paypal IPN
    header('location:https://www.sandbox.paypal.com/cgi-bin/webscr'.$querystring);
    exit();
 
}else{
 
    // Response from Paypal
 
    // read the post from PayPal system and add 'cmd'
    $req = 'cmd=_notify-validate';
    foreach ($_POST as $key => $value) {
        $value = urlencode(stripslashes($value));
        $value = preg_replace('/(.*[^%^0^D])(%0A)(.*)/i','${1}%0D%0A${3}',$value);// IPN fix
        $req .= "&$key=$value";
    }
 
    // post back to PayPal system to validate
    $header = "POST /cgi-bin/webscr HTTP/1.0\r\n";
    $header .= "Content-Type: application/x-www-form-urlencoded\r\n";
    $header .= "Content-Length: " . strlen($req) . "\r\n\r\n";
 
    $fp = fsockopen ('ssl://www.sandbox.paypal.com', 443, $errno, $errstr, 30);    
 
    // assign posted variables to local variables
    $data['item_name']            = $_POST['item_name'];
    $data['item_number']         = $_POST['item_number'];
    $data['payment_status']     = $_POST['payment_status'];
    $data['payment_amount']     = $_POST['mc_gross'];
    $data['payment_currency']    = $_POST['mc_currency'];
    $data['txn_id']                = $_POST['txn_id'];
    $data['receiver_email']     = $_POST['receiver_email'];
    $data['payer_email']         = $_POST['payer_email'];
   /* $data['custom']             = $_POST['custom']; */
 
 
 
    if (!$fp) {
        // HTTP ERROR
     echo "http error";// HTTP ERROR
    } else {    
 
        fputs ($fp, $header . $req);
        while (!feof($fp)) {
            $res = fgets ($fp, 1024);
            if (strcmp($res, "VERIFIED") == 0) {
 
                // Used for debugging
                @mail("myemail.co.uk", "PAYPAL DEBUGGING", "Verified Response<br />data = <pre>".print_r($post, true)."</pre>");
 
                // Validate payment (Check unique txnid & correct price)
                $valid_txnid = check_txnid($data['txn_id']);
                $valid_price = check_price($data['payment_amount'], $data['item_number']);
                // PAYMENT VALIDATED & VERIFIED!
                if($valid_txnid && $valid_price){                
                    $orderid = updatePayments($data);        
                    if($orderid){                    
                        // Payment has been made & successfully inserted into the Database                                
                    }else{  
 
                    @mail("[e-mail]", "PAYPAL DEBUGGING", "Verified Response<br />data = <pre>".print_r($post, true)."</pre>");
 
                        // Error inserting into DB
                        // E-mail admin or alert user
                    }
                }else{                    
                    // Payment made but data has been changed
                    // E-mail admin or alert user
                }                        
 
            }else if (strcmp ($res, "INVALID") == 0) {
 
                // PAYMENT INVALID & INVESTIGATE MANUALY! 
                // E-mail admin or alert user
 
                // Used for debugging
                @mail("myemail.com", "PAYPAL DEBUGGING", "Invalid Response<br />data = <pre>".print_r($post, true)."</pre>");
            }        
        }        
    fclose ($fp);
    }    
}
?>
 
 

functions.php....

 
<?php
  // functions.php    // table customerdetails
function check_txnid($tnxid){
    global $link;
    return true;
    $valid_txnid = true;
    //get result set
    $sql = mysql_query("SELECT * FROM payments WHERE txnid = '$tnxid'", $link)or die(mysql_error());
    if($row = mysql_fetch_array($sql)) {
        $valid_txnid = false;
    }
    return $valid_txnid;
}
 
function check_price($price, $id){
    $valid_price = false;
 
    return true;
}
 
function updatePayments($data){
    global $link;
    if(is_array($data)){
        $sql = mysql_query("INSERT INTO payments (txnid, payment_amount, payment_status, itemid, createdtime) VALUES (
                '".$data['txn_id']."' ,
                '".$data['payment_amount']."' ,
                '".$data['payment_status']."' ,
                '".$data['item_number']."' ,
                '".date("Y-m-d H:i:s")."'
                )", $link)or die(mysql_error());
    return mysql_insert_id($link)or die(mysql_error());;
    }
}
 
?>