IPN is a behind the scenes feature. Once the transaction complets, PayPal will send a POST of the transaction details back to your IPN script. You read the values and do a POST back to PayPal to verify that it came from PayPal. Then PayPal confirms if it is valid or not. Then based on that response you can do what ever you need to with transaction details that were posted to your script. The example below is a PHP example for an IPN script.
<?php
// Revision Notes
// 11/04/11 - changed post back url from https://www.paypal.com/cgi-bin/webscr to https://ipnpb.paypal.com/cgi-bin/webscr
// For more info see below:
// https://www.x.com/content/bulletin-ip-address-expansion-paypal-services
// "ACTION REQUIRED: if you are using IPN (Instant Payment Notification) for Order Management and your IPN listener script is behind a firewall that uses ACL (Access Control List) rules which restrict outbound traffic to a limited number of IP addresses, then you may need to do one of the following:
// To continue posting back to https://www.paypal.com to perform IPN validation you will need to update your firewall ACL to allow outbound access to *any* IP address for the servers that host your IPN script
// OR Alternatively, you will need to modify your IPN script to post back IPNs to the newly created URL https://ipnpb.paypal.com using HTTPS (port 443) and update firewall ACL rules to allow outbound access to the ipnpb.paypal.com IP ranges (see end of message)."
/////////////////////////////////////////////////
/////////////Begin Script below./////////////////
/////////////////////////////////////////////////
// read the post from PayPal system and add 'cmd'
$req = 'cmd=_notify-validate';
foreach ($_POST as $key => $value) {
$value = urlencode(stripslashes($value));
$req .= "&$key=$value";
}
// post back to PayPal system to validate
$header = "POST /cgi-bin/webscr HTTP/1.1
";
$header .= "Content-Type: application/x-www-form-urlencoded
";
$header .= "Content-Length: " . strlen($req) . "
";
// If testing on Sandbox use:
//$fp = fsockopen ('ssl://www.sandbox.paypal.com', 443, $errno, $errstr, 30);
$fp = fsockopen ('ssl://ipnpb.paypal.com', 443, $errno, $errstr, 30);
// assign posted variables to local variables
$item_name = $_POST['item_name'];
$business = $_POST['business'];
$item_number = $_POST['item_number'];
$payment_status = $_POST['payment_status'];
$mc_gross = $_POST['mc_gross'];
$payment_currency = $_POST['mc_currency'];
$txn_id = $_POST['txn_id'];
$receiver_email = $_POST['receiver_email'];
$receiver_id = $_POST['receiver_id'];
$quantity = $_POST['quantity'];
$num_cart_items = $_POST['num_cart_items'];
$payment_date = $_POST['payment_date'];
$first_name = $_POST['first_name'];
$last_name = $_POST['last_name'];
$payment_type = $_POST['payment_type'];
$payment_status = $_POST['payment_status'];
$payment_gross = $_POST['payment_gross'];
$payment_fee = $_POST['payment_fee'];
$settle_amount = $_POST['settle_amount'];
$memo = $_POST['memo'];
$payer_email = $_POST['payer_email'];
$txn_type = $_POST['txn_type'];
$payer_status = $_POST['payer_status'];
$address_street = $_POST['address_street'];
$address_city = $_POST['address_city'];
$address_state = $_POST['address_state'];
$address_zip = $_POST['address_zip'];
$address_country = $_POST['address_country'];
$address_status = $_POST['address_status'];
$item_number = $_POST['item_number'];
$tax = $_POST['tax'];
$option_name1 = $_POST['option_name1'];
$option_selection1 = $_POST['option_selection1'];
$option_name2 = $_POST['option_name2'];
$option_selection2 = $_POST['option_selection2'];
$for_auction = $_POST['for_auction'];
$invoice = $_POST['invoice'];
$custom = $_POST['custom'];
$notify_version = $_POST['notify_version'];
$verify_sign = $_POST['verify_sign'];
$payer_business_name = $_POST['payer_business_name'];
$payer_id =$_POST['payer_id'];
$mc_currency = $_POST['mc_currency'];
$mc_fee = $_POST['mc_fee'];
$exchange_rate = $_POST['exchange_rate'];
$settle_currency = $_POST['settle_currency'];
$parent_txn_id = $_POST['parent_txn_id'];
$pending_reason = $_POST['pending_reason'];
$reason_code = $_POST['reason_code'];
// subscription specific vars
$subscr_id = $_POST['subscr_id'];
$subscr_date = $_POST['subscr_date'];
$subscr_effective = $_POST['subscr_effective'];
$period1 = $_POST['period1'];
$period2 = $_POST['period2'];
$period3 = $_POST['period3'];
$amount1 = $_POST['amount1'];
$amount2 = $_POST['amount2'];
$amount3 = $_POST['amount3'];
$mc_amount1 = $_POST['mc_amount1'];
$mc_amount2 = $_POST['mc_amount2'];
$mc_amount3 = $_POST['mcamount3'];
$recurring = $_POST['recurring'];
$reattempt = $_POST['reattempt'];
$retry_at = $_POST['retry_at'];
$recur_times = $_POST['recur_times'];
$username = $_POST['username'];
$password = $_POST['password'];
//auction specific vars
$for_auction = $_POST['for_auction'];
$auction_closing_date = $_POST['auction_closing_date'];
$auction_multi_item = $_POST['auction_multi_item'];
$auction_buyer_id = $_POST['auction_buyer_id'];
//DB connect creds and email
$notify_email = "MyEmail@MySite.com"; //email address to which debug emails are sent to
$DB_Server = "MyServer"; //your MySQL Server
$DB_Username = "MyDBuser"; //your MySQL User Name
$DB_Password = "MyDMpassword"; //your MySQL Password
$DB_DBName = "MyDatabase"; //your MySQL Database Name
if (!$fp) {
// HTTP ERROR
} else {
fputs ($fp, $header . $req);
while (!feof($fp)) {
$res = fgets ($fp, 1024);
if (strcmp ($res, "VERIFIED") == 0) {
//create MySQL connection
$Connect = @mysql_connect($DB_Server, $DB_Username, $DB_Password)
or die("Couldn't connect to MySQL:<br>" . mysql_error() . "<br>" . mysql_errno());
//select database
$Db = @mysql_select_db($DB_DBName, $Connect)
or die("Couldn't select database:<br>" . mysql_error(). "<br>" . mysql_errno());
$fecha = date("m")."/".date("d")."/".date("Y");
$fecha = date("Y").date("m").date("d");
//check if transaction ID has been processed before
$checkquery = "select txnid from paypal_payment_info where txnid='".$txn_id."'";
$sihay = mysql_query($checkquery) or die("Duplicate txn id check query failed:<br>" . mysql_error() . "<br>" . mysql_errno());
$nm = mysql_num_rows($sihay);
if ($nm == 0){
//execute query
if ($txn_type == "cart"){
$strQuery = "insert into paypal_payment_info(paymentstatus,buyer_email,firstname,lastname,street,city,state,zipcode,country,mc_gross,mc_fee,memo,paymenttype,paymentdate,txnid,pendingreason,reasoncode,tax,datecreation) values ('".$payment_status."','".$payer_email."','".$first_name."','".$last_name."','".$address_street."','".$address_city."','".$address_state."','".$address_zip."','".$address_country."','".$mc_gross."','".$mc_fee."','".$memo."','".$payment_type."','".$payment_date."','".$txn_id."','".$pending_reason."','".$reason_code."','".$tax."','".$fecha."')";
$result = mysql_query($strQuery) or die("Cart - paypal_payment_info, Query failed:<br>" . mysql_error() . "<br>" . mysql_errno());
for ($i = 1; $i <= $num_cart_items; $i++) {
$itemname = "item_name".$i;
$itemnumber = "item_number".$i;
$on0 = "option_name1_".$i;
$os0 = "option_selection1_".$i;
$on1 = "option_name2_".$i;
$os1 = "option_selection2_".$i;
$quantity = "quantity".$i;
$struery = "insert into paypal_cart_info(txnid,itemnumber,itemname,os0,on0,os1,on1,quantity,invoice,custom) values ('".$txn_id."','".$_POST[$itemnumber]."','".$_POST[$itemname]."','".$_POST[$on0]."','".$_POST[$os0]."','".$_POST[$on1]."','".$_POST[$os1]."','".$_POST[$quantity]."','".$invoice."','".$custom."')";
$result = mysql_query($struery) or die("Cart - paypal_cart_info, Query failed:<br>" . mysql_error() . "<br>" . mysql_errno());
}
}
else{
$strQuery = "insert into paypal_payment_info(paymentstatus,buyer_email,firstname,lastname,street,city,state,zipcode,country,mc_gross,mc_fee,itemnumber,itemname,os0,on0,os1,on1,quantity,memo,paymenttype,paymentdate,txnid,pendingreason,reasoncode,tax,datecreation) values ('".$payment_status."','".$payer_email."','".$first_name."','".$last_name."','".$address_street."','".$address_city."','".$address_state."','".$address_zip."','".$address_country."','".$mc_gross."','".$mc_fee."','".$item_number."','".$item_name."','".$option_name1."','".$option_selection1."','".$option_name2."','".$option_selection2."','".$quantity."','".$memo."','".$payment_type."','".$payment_date."','".$txn_id."','".$pending_reason."','".$reason_code."','".$tax."','".$fecha."')";
$result = mysql_query("insert into paypal_payment_info(paymentstatus,buyer_email,firstname,lastname,street,city,state,zipcode,country,mc_gross,mc_fee,itemnumber,itemname,os0,on0,os1,on1,quantity,memo,paymenttype,paymentdate,txnid,pendingreason,reasoncode,tax,datecreation) values ('".$payment_status."','".$payer_email."','".$first_name."','".$last_name."','".$address_street."','".$address_city."','".$address_state."','".$address_zip."','".$address_country."','".$mc_gross."','".$mc_fee."','".$item_number."','".$item_name."','".$option_name1."','".$option_selection1."','".$option_name2."','".$option_selection2."','".$quantity."','".$memo."','".$payment_type."','".$payment_date."','".$txn_id."','".$pending_reason."','".$reason_code."','".$tax."','".$fecha."')") or die("Default - paypal_payment_info, Query failed:<br>" . mysql_error() . "<br>" . mysql_errno());
}
// send an email in any case
echo "Verified";
mail($notify_email, "VERIFIED IPN", "$res
$req
$strQuery
$struery
$strQuery2");
}
else {
// send an email
mail($notify_email, "VERIFIED DUPLICATED TRANSACTION", "$res
$req
$strQuery
$struery
$strQuery2");
}
//subscription handling branch
if ( $txn_type == "subscr_signup" || $txn_type == "subscr_payment" ) {
// insert subscriber payment info into paypal_payment_info table
$strQuery = "insert into paypal_payment_info(paymentstatus,buyer_email,firstname,lastname,street,city,state,zipcode,country,mc_gross,mc_fee,memo,paymenttype,paymentdate,txnid,pendingreason,reasoncode,tax,datecreation) values ('".$payment_status."','".$payer_email."','".$first_name."','".$last_name."','".$address_street."','".$address_city."','".$address_state."','".$address_zip."','".$address_country."','".$mc_gross."','".$mc_fee."','".$memo."','".$payment_type."','".$payment_date."','".$txn_id."','".$pending_reason."','".$reason_code."','".$tax."','".$fecha."')";
$result = mysql_query($strQuery) or die("Subscription - paypal_payment_info, Query failed:<br>" . mysql_error() . "<br>" . mysql_errno());
// insert subscriber info into paypal_subscription_info table
$strQuery2 = "insert into paypal_subscription_info(subscr_id , sub_event, subscr_date ,subscr_effective,period1,period2, period3, amount1 ,amount2 ,amount3, mc_amount1, mc_amount2, mc_amount3, recurring, reattempt,retry_at, recur_times, username ,password, payment_txn_id, subscriber_emailaddress, datecreation) values ('".$subscr_id."', '".$txn_type."','".$subscr_date."','".$subscr_effective."','".$period1."','".$period2."','".$period3."','".$amount1."','".$amount2."','".$amount3."','".$mc_amount1."','".$mc_amount2."','".$mc_amount3."','".$recurring."','".$reattempt."','".$retry_at."','".$recur_times."','".$username."','".$password."', '".$txn_id."','".$payer_email."','".$fecha."')";
$result = mysql_query($strQuery2) or die("Subscription - paypal_subscription_info, Query failed:<br>" . mysql_error() . "<br>" . mysql_errno());
mail($notify_email, "VERIFIED IPN", "$res
$req
$strQuery
$struery
$strQuery2");
}
}
// if the IPN POST was 'INVALID'...do this
else if (strcmp ($res, "INVALID") == 0) {
// log for manual investigation
mail($notify_email, "INVALID IPN", "$res
$req");
}
}
fclose ($fp);
}
?>
