php代码错误警告：Digital_Signature :: CreateSign（）的声明

Question

 function CreateSign()
{
$rsa_obj = new Crypt_RSA(array('private_key' => $this->_privateKey));
$this->check_error($rsa_obj);
return $rsa_obj->createSign($this->_document);
}

此代码显示此错误

Warning: Declaration of Digital_Signature::CreateSign() should be compatible with Crypt_RSA::createSign($document, $private_key = NULL, $hash_func = NULL) in /var/www/html/shares/digital_signature.php on line 49

任何人都可以提供帮助

Answer 1

父类和子类中的两个函数都应具有相同的参数，其参数的默认值也相同