public function setAuthSubPrivateKey($key, $passphrase = null) { if ($key != null && !function_exists('openssl_pkey_get_private')) { require_once 'Zend/Gdata/App/InvalidArgumentException.php'; throw new Zend_Gdata_App_InvalidArgumentException('You cannot enable secure AuthSub if the openssl module ' . 'is not enabled in your PHP installation.'); } $this->_authSubPrivateKeyId = openssl_pkey_get_private($key, $passphrase); return $this; }