Integrating Paypal Expresscheckout in PHP

Question

for some time I have been researching how to integrate Paypal in my online stores, the ones I myself build from 0 until the final stage that is the payment, but when I went to the Paypal site to learn more about the integration I faced some problems, which was to interpret the NVP (Name-Pair-Value), in order to connect with the Paypal API and define the methods or requests to start up to complete the purchase, but then a series of researches and studies of Opensource scripts, although they seem complex I managed to understandall in all, and I was able to integrate Paypal Expresscheckout into my store.

The main questions are:

How do I connect to the Paypal API without compromising my credentials ?

How I define the methods required for Expresscheckout ?

How do I know that the purchase was made or completed without errors ?

Answer 1

The Expresscheckout is used to perform secure purchase/sales on the Paypal website and at the end of the purchase the customer returns to the site of the user or company.

To understand how Paypal Expresscheckout works, you have to first realize its workflow.

Shop -> Request (Setexpresscheckout) -> Server Responds With Token -> HTTP Redirect with &token= -> ->Return URL + TOKEN -> Request (Getexpresscheckoutdetails) -> Answer -> Request (Doexpressoutpcheckayment) -> Answer (Success/Failure) -> Complete Order

Connecting with the Paypal API.

     <?php
     class paypal{
//Função de conexão com a API
function api($comando,$param){
    $api = 'https://api-3t.sandbox.paypal.com/nvp'; # URL para o modo sandbox
    $api_user = urlencode('<API_USUARIO>');
    $api_senha = urlencode('<API_SENHA>');
    $api_assinatura = urlencode('<API_ASSINATURA>');
    $api_versao = urlencode('109.0'); # Esta é a versão da API a ser utilizada
    $i = curl_init();
    # Definimos uma cabeçalho para a requisição
    curl_setopt($i, CURLOPT_URL, $api); 
    curl_setopt($i, CURLOPT_VERBOSE, 1);
    #Desactivar a verificação do servidor e do peer
    curl_setopt($i, CURLOPT_SSL_VERIFYPEER, FALSE);
    curl_setopt($i, CURLOPT_SSL_VERIFYHOST, FALSE);

    curl_setopt($i, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($i, CURLOPT_POST, 1);

    //Passando os parâmetros da API
    $nvp = "METHOD=$comando&VERSION=$api_versao&PWD=$api_senha&USER=$api_user&SIGNATURE=$api_assinatura$param";

    //Definindo o nvp como campo POST do cURL
    curl_setopt($i, CURLOPT_POSTFIELDS, $nvp);
    $resposta = curl_exec($i);
    curl_close($i);

    if(!$resposta){
        exit("Erro do $comando ".curl_error($i)."(".curl_errno($i).")");
        }
    #Aqui transformamos a nossa URL numa array associativa
    $respostaP = $this->nvp($resposta);
    if(0 == sizeof($respostaP) || !array_key_exists('ACK',$respostaP)){
        exit("HTTP resposta inválida do servidor($nvp) para $api");
        }

    return $respostaP;
    }
    // função para converter a resposta da cURL em array
    function nvp($resposta){
    $i = explode('&',$resposta);
    $respostaP = array();
    foreach($i as $key=>$value){
    $d = explode('=',$value);
    if(sizeof($d)>1){
    $respostaP[$d[0]] = $d[1];
     }
    }
    return $respostaP;
    }


}

?>

After defining the connection variables, you can then define the methods to be of the call to start and complete the purchase.

    <?php

    //Iniciamos a sessão
    session_start();

   //Incluimos a nossa classe 
   include_once('paypal.php');

   //Se for utilizar o modo live, deixe a variavel $paypalmodo com o ponto(.) apenas
   $paypalmodo = '.sandbox';
   $moeda = 'USD';
   $urlRetorno = 'http://site.com/retorno';
   $urlCancela = 'http://site.com/cancela';

   //Parte que trata do SetExpressCheckout
   if(isset($_POST) && !empty($_POST)){

$itemNome = $_POST['itemNome'];
$itemPreco = $_POST['itemPreco'];
$itemQnt = $_POST['itemQnt'];
$itemTotal = ($itemPreco*$itemQnt);

$taxa = 1.50;

$total = ($itemTotal + $taxa);

$nvpData = '&METHOD=SetExpressCheckout'.
           '&RETURNURL='.urlencode($urlRetorno).
           '&CANCELURL='.urlencode($urlCancela).
           '&PAYMENTREQUEST_0_PAYMENTACTION='.urlencode('Sale').
           '&L_PAYMENTREQUEST_0_NAME0='.urlencode($itemNome).

           '&L_PAYMENTREQUEST_0_AMT0='.urlencode($itemTotal).
           '&L_PAYMENTREQUEST_0_QTY0='.urlencode($itemQnt).

           '&NOSHIPPING=0'.

           '&PAYMENTREQUEST_0_ITEMAMT='.urlencode($itemTotal).
           '&PAYMENTREQUEST_0_TAXAMT='.urlencode($taxa).
           '&PAYMENTREQUEST_0_AMT='.urlencode($total).
           '&PAYMENTREQUEST_0_CURRENCYCODE='.urlencode($moeda).

           '&LOCALECODE=BR'.
           '&LOGOIMG='.'http://site.com/logo_a_utilizar_caso_tenha.jpg'.
           '&CARTBORDERCOLOR=45D765'.
           '&ALLOWNOTE=1';

//Definindo as as variaveis de SESSAO
$_SESSION['itemNome'] = $itemNome;
$_SESSION['itemPreco'] = $itemPreco;
$_SESSION['itemQnt'] = $itemQnt;
$_SESSION['itemTotal'] = $itemTotal;

$_SESSION['taxa'] = $taxa;
$_SESSION['total'] = $total;


//Instanciado a class paypal e chamando a função  de conexão api('SetExpressCheckout','paramentros_da_url') 
$paypal = new paypal();
$resposta = $paypal->api('SetExpressCheckout',$nvpData);

if('SUCCESS' == strtoupper($resposta['ACK']) || 'SUCCESSWITHWARNING' == strtoupper($resposta['ACK'])){
    //Url de redirectionamento com os parâmetros inseridos
    $paypalUrl = 'https://www'.$paypalmodo.'.paypal.com/cgi-bin/webscr?cmd=_express-checkout&token='.$resposta["TOKEN"].'';
    header('Location:'.$paypalUrl);
    } else {
        echo '<div style="color:red"><b>Erro : </b>'.urldecode($resposta["L_LONGMESSAGE0"]).'</div>';
        }
    echo '<pre>';
        print_r($resposta);
    echo '</pre>';

}

    //Parte que trata do DoExpressCheckout

    if(isset($_GET['token']) && isset($_GET['PayerID'])){

$token = $_GET['token'];
$payer_id = $_GET['PayerID'];

$itemNome = $_SESSION['itemNome'];
$itemNum = $_SESSION['itemNum'];
$itemQnt = $_SESSION['itemQnt'];
$itemTotal = $_SESSION['itemTotal'];

$taxa = $_SESSION['taxa'];
$total = $_SESSION['total'];

$nvpData = '&TOKEN='.urlencode($token).
           '&PAYERID='.urlencode($payer_id).
           '&PAYMENTREQUEST_0_PAYMENTACTION='.urlencode("Sale").

           '&L_PAYMENTREQUEST_0_NAME0='.urlencode($itemNome).
           '&L_PAYMENTREQUEST_0_AMT0='.urlencode($itemPreco).
           '&L_PAYMENTREQUEST_0_QTY0='.urlencode($itemQnt).

           '&PAYMENTREQUEST_0_ITEMAMT='.urlencode($itemTotal).
           '&PAYMENTREQUEST_0_TAXAMT='.urlencode($taxa).
           '&PAYMENTREQUEST_0_AMT='.urlencode($total).
           '&PAYMENTREQUEST_0_CURRENCYCODE='.urlencode($moeda);


//Instanciando a class paypal e chamando a função api('DoExpressCheckoutPayment','paramentros_da_url')         
$paypal = new paypal();
$resposta = $paypal->api('DoExpressCheckoutPayment',$nvpData);

if('SUCCESS' == strtoupper($resposta['ACK']) || 'SUCCESSWITHWARNING' == strtoupper($resposta['ACK'])){

    echo "<h2 style='color:green;'>Concluído</h2>";
    echo "ID da sua compra: ".$resposta['PAYMENTINFO_0_TRANSACTIONID'];

    if('Completed' == $resposta['PAYMENTINFO_0_PAYMENTSTATUS']){
        session_destroy();
        echo '<div style="color:green">Pagamento completo! Obrigado pela compra.</div>';
        } else if('Peding' == $resposta['PAYMENTINFO_0_PAYMENTSTATUS']){
            echo '<div style="color:red">Transação completa, mas o pagamento precisa de ser aprovado manualmente na sua <a target="_new" href="http://www.paypal.com">Conta do PayPal</a></div>';
            }

    //Parte Responsavel por pegar os detalhes da transação
    //Esta parte só é exibida se a transação for efectuada com sucesso ou retornar Success
    $nvpData = '&TOKEN='.urlencode($token);
    $paypal = new paypal();
    $resposta = $paypal->api('GetExpressCheckoutDetails',$nvpData);

if('SUCCESS' == strtoupper($resposta['ACK']) || 'SUCCESSWITHWARNING' == strtoupper($resposta['ACK'])){


                echo '<br /><b>Coisas para adicionar no banco de dados :</b><br /><pre>';

                echo '<pre>';
                print_r($resposta);
                echo '</pre>';
            } else  {
                echo '<div style="color:red"><b>GetTransactionDetails failed:</b>'.urldecode($resposta["L_LONGMESSAGE0"]).'</div>';
                echo '<pre>';
                print_r(urldecode($resposta));
                echo '</pre>';


        }

    } else {
        //Esta parte é responsavel por verificar o erro caso a chamada api('DoExpressCheckoutPayment','paramentros') falhe.
        echo "Erro :".urldecode($resposta['L_LONGMESSAGE0']);
        echo "<pre>";
        foreach($resposta as $id=>$valor){
            echo "<div style='color:red; border:2px solid #ccc;'>[".$id."] => ".urldecode($valor)."<br/></div>";
            }
        echo "</pre>";
        }



}
    ?>

And finally the page responsible for providing the data about the item by the POST method.

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>Site.com(LOJA)</title>
    <style type="text/css">
    body {background-color:#D7D7D7;}
    *{font-family: Tahoma, Geneva, sans-serif;}
    h1 {text-align:center; color:#333; font-family: "Trebuchet MS", Arial, Helvetica, sans-serif;}
    h4 {color:#333; font-family: "Trebuchet MS", Arial, Helvetica, sans-serif;}
    table {border:1px solid #666; border-radius:5px 5px 5px 5px; box-shadow:1px 0px 1px #999 inset; background-color:#F2F2F2; margin:0 auto;}
    input {border:1px solid #333; border-radius:4px 5px 5px 5px; box-shadow:1px 0px 1px #999 inset; padding:5px; margin-top:2px;}
    input:hover {background-color:#FFF; transition:ease-in-out 0.4s; box-shadow:1px 0px 1px #CCC inset;}
    </style>
    </head>

    <body>
    <?php
    $moeda = 'USD';
    ?>
    <h1>Site.com</h1>
    <table border="0" cellpadding="4">
    <tr>
    <td width="70%"><h4>Bilhetes Platina</h4>(Se vai ao concerto logo a noite, esta é a  sua melhor chance de ficar na fila V.I.P)</td>
    <td width="30%">
    <form method="post" action="checkout.php">
<input type="hidden" name="itemNome" value="Bilhetes Platina" /> 
<input type="hidden" name="itemPreco" value="20.00" />
    Quantidade : <select name="itemQnt"><option value="1">1</option><option value="2">2</option><option value="3">3</option></select> 
    <input type="submit"  value="Comprar (20.00 <?php echo $moeda; ?>)" />
    </form>
    </td>
    </tr>
    </table>
    </body>
    </html>

Answer 2

I believe that explaining all the steps of creating an API (Application Program Interface) is not feasible.

If you want to spend money to learn, there are some courses like this: Course Creating and Using Apis in PHP.

Otherwise, I recommend watching video lessons from Youtube like this: PHP Tutorial: Developer API [part 00].

As questions arise, you can ask here at Stackoverflow.