<form id="wps-bn" action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post" >

<!--Tipo do botão-->

<input type="hidden" name="cmd" value="_xclick" />

<!--Vendedor e URL de retorno, cancelamento e notificação-->

<input type="hidden" name="business" value="atendimento-facilitator@meusite.com" />

<input type="hidden" name="return" value="http://meusite/paypal/ipn" />

<input type="hidden" name="cancel" value="http://meusite/action/cancelamento" />

<input type="hidden" name="notify_url" value="http://meusite/notificacao" />

<!--Internacionalização e localização da página de pagamento-->

<input type="hidden" name="charset" value="utf-8" />

<input type="hidden" name="lc" value="BR" />

<input type="hidden" name="country_code" value="BR" />

<input type="hidden" name="currency_code" value="BRL" />

<!--Informações sobre o produto e seu valor-->

<input type="hidden" name="amount" value="12.34" />

<input type="hidden" name="item_name" value="Servico" />

<input type="hidden" name="quantity" value="1" />

<!--Botão para submissão do formulário-->

<input type="image" src="https://www.paypalobjects.com/pt_BR/BR/i/btn/btn_buynowCC_LG.gif" border="0" />

$total = '150.95'; //VALOR TOTAL DA COMPRA
$id_compra = '123'; //ID DA COMPRA

$nvp = array(
    'PAYMENTREQUEST_0_AMT'              => $total,
    'PAYMENTREQUEST_0_CURRENCYCODE'     => 'BRL',
    'PAYMENTREQUEST_0_PAYMENTACTION'    => 'Sale',
    'PAYMENTREQUEST_0_CUSTOM'           => $id_compra,
    'L_PAYMENTREQUEST_0_NAME0'          => 'Pedido número '.$id_compra,
    'L_PAYMENTREQUEST_0_DESC0'          => 'Pagamento referente ao pedido '.$id_compra,
    'L_PAYMENTREQUEST_0_AMT0'           => $total,
    'L_PAYMENTREQUEST_0_QTY0'           => 1,
    'L_PAYMENTREQUEST_0_ITEMAMT'        => $total,
    // 'RETURNURL'                         => 'http://beta.socioteca2014.com/advertisement/retorno',
    'RETURNURL'                         => 'meusite.com/paypal/ipn',
    'CANCELURL'                         => 'https://www.seusite.com.br/cancelamento.php',
    'METHOD'                            => 'SetExpressCheckout',
    'VERSION'                           => '108.0',
    'PWD'                               => '',
    'USER'                              => '',
    'SIGNATURE'                         => '',
    'CMD' => '_xclick'
);


$curl = curl_init();

curl_setopt( $curl , CURLOPT_URL , 'https://api-3t.sandbox.paypal.com/nvp' );
curl_setopt( $curl , CURLOPT_SSL_VERIFYPEER , false );
curl_setopt( $curl , CURLOPT_RETURNTRANSFER , 1 );
curl_setopt( $curl , CURLOPT_POST , 1 );
curl_setopt( $curl , CURLOPT_POSTFIELDS , http_build_query( $nvp ) );

$response = urldecode( curl_exec( $curl ) );
$responseNvp = array();

curl_close( $curl );

if ( preg_match_all( '/(?<name>[^=]+)=(?<value>[^&]+)&?/' , $response , $matches ) ) {
    foreach ( $matches[ 'name' ] as $offset => $name ) {
        $responseNvp[ $name ] = $matches[ 'value' ][ $offset ];
    }
}

if ( isset( $responseNvp[ 'ACK' ] ) && $responseNvp[ 'ACK' ] == 'Success' ) {
    $paypalURL = 'https://www.sandbox.paypal.com/cgi-bin/webscr';
    $query = array(
        'cmd'    => '_express-checkout',
        'token'    => $responseNvp[ 'TOKEN' ]
    );

    forward($paypalURL . '?' . http_build_query( $query ) );
} else {
    echo 'Falha na transação';
}

$sandbox = true;

error_log('IPN triggered: ' . print_r($_POST,1));
$txn = (object) $_POST;

// This IPN listener reads IPN msgs sent from PayPal, verifies the msg, and processes
// the data by posting the IPN message fields and values to the browser screen.

// read the IPN msg from PayPal and add 'cmd' for your verification request
$req = 'cmd=_notify-validate';

// append the IPN msg, in NVP format, to your verification request
foreach ($_POST as $key => $value) {
    $value = urlencode(stripslashes($value));
    $req .= "&$key=$value";
}

// set up the headers for your verification request
// POST your verification requests to PayPal (here, the Sandbox)
$header  = "POST /cgi-bin/webscr HTTP/1.0rn";

if ($sandbox) {
    $header .= "Host: www.sandbox.paypal.com:443rn";
    $fsock = 'ssl://www.sandbox.paypal.com';
}
else {
    $header .= "Host: ipnpb.paypal.com:443rn";      // endpoint for Live apps
    $fsock = 'ssl://ipnpb.paypal.com';
}

$header .= "Content-Type: application/x-www-form-urlencodedrn";
$header .= "Content-Length: " . strlen($req) . "rnrn";

// open the socket
// $fp = fsockopen ('ssl://www.sandbox.paypal.com', 443, $errno, $errstr, 30);
$fp = fsockopen ($fsock, 443, $errno, $errstr, 30);

if (!$fp) {
    // HTTP error
    error_log("Paypal IPN ERROR:: HTTP socket error! Unable to open URL");
    die('error $fp');
}
else {
    // POST verification request
    fputs ($fp, $header . $req);
while (!feof($fp)) {
    $res = fgets ($fp, 1024);

    if (strcmp ($res, "VERIFIED") == 0) {
            // trigger plugin hook for individual plugins to have an option to save the ipn first
            $result = elgg_trigger_plugin_hook('paypal', 'ipn_log', array('txn' => $txn), false);

            if (!$result) {
                // no plugins logged the transaction, log it to the site
                //
                paypal_log_ipn(elgg_get_logged_in_user_entity(), $txn);
            }
    }
    else if (strcmp ($res, "INVALID") == 0) {

        // invalid - do nothing for now
        // IPN invalid, log for manual investigation
        paypal_log_ipn(elgg_get_logged_in_user_entity(), $txn);
    }
}

fclose ($fp);
}
exit;