Código PHP:
$config = array('sslverifypeer'=>FALSE);
$params = array(
'USER'=>'asociacion.pfc1_api1.gmail.com',
'PWD'=>'xxxxxxxxxxx',
'SIGNATURE'=>'xxxxxxxxxxxx',
'METHOD' => 'RefundTransaction',
'TRANSACTIONID' => $transactionId,
'REFUNDTYPE' => 'Full',
'CURRENCYCODE'=>'EUR',
'VERSION'=>'51.0',
);
$url ='https://api-3t.sandbox.paypal.com/nvp';
$client = new Zend_Http_Client($url,$config);
$client->setMethod(Zend_Http_Client::POST);
$client->setParameterPost($Params);
echo $response = $client->request();
ACK=Failure&L_ERRORCODE0=81002&L_SHORTMESSAGE0=Uns pecified%20Method&L_LONGMESSAGE0=Method%20Specifie d%20is%20not%20Supported&L_SEVE
¿Alguien me puede ayudar?