PHP 5.6 Connection SFTP with Private Key

Question

why can't I connect sftp with private key, always get message (SSH public key authentication failed: Invalid Username/PublicKey combination) for private key this tried with filezilla and works fine. here i have tried using cURL & ssh2 but all are invalid. can anyone give a solution?

            $local_filename = $this->stock;
            $fp = fopen($local_filename, 'r');
            $sftp_server =  $this->ipServer . $this->pathServer . '/STOCK.zip';

            $curl = curl_init();
            curl_setopt($curl, CURLOPT_UPLOAD, TRUE);
            curl_setopt($curl, CURLOPT_HEADER, TRUE);
            curl_setopt($curl, CURLOPT_VERBOSE, TRUE);
            curl_setopt($curl, CURLOPT_RETURNTRANSFER, TRUE);
            curl_setopt($curl, CURLOPT_PROTOCOLS, CURLPROTO_SFTP);
            curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, 2);
            curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, FALSE);
            curl_setopt($curl, CURLOPT_NOPROGRESS, FALSE);
            curl_setopt($curl, CURLOPT_FOLLOWLOCATION, TRUE);

            $trace = tempnam(dirname($local_filename), 'temp_curl_');
            $fptrace = fopen($trace, 'w');
            curl_setopt($curl, CURLOPT_FILE, $fptrace);
            curl_setopt($curl, CURLOPT_STDERR, $fptrace);

            curl_setopt($curl, CURLOPT_URL, 'sftp://@' . $sftp_server);
            curl_setopt($curl, CURLOPT_PORT, $this->portServer);
            curl_setopt($curl, CURLOPT_USERPWD, $this->username . ':');
            curl_setopt($curl, CURLOPT_SSH_AUTH_TYPES, CURLSSH_AUTH_PUBLICKEY);
            curl_setopt($curl, CURLOPT_SSH_PUBLIC_KEYFILE, $this->publicKey);
            curl_setopt($curl, CURLOPT_SSH_PRIVATE_KEYFILE, $this->privateKey);
            curl_setopt($curl, CURLOPT_KEYPASSWD, '');
            curl_setopt($curl, CURLOPT_INFILESIZE, filesize($local_filename));
            curl_setopt($curl, CURLOPT_INFILE, $fp);

            $start_error_no = curl_errno($curl);
            $valid_operation = curl_exec($curl);
            $final_error_no = curl_errno($curl);
            curl_close($curl);
            fclose($fp);
            fclose($fptrace);

            echo '<pre>trace:', file_get_contents($trace), '<hr>';
            var_dump($valid_operation);
            unlink($trace);
            die();```

and

        $session = @ssh2_connect($this->ipServer, 22, ['hostkey' => 'ssh-rsa']);
        if (@ssh2_auth_pubkey_file($session, $this->username, $this->publicKey, $this->privateKey, 'password')) {
            echo "Public Key Authentication Successful\n";
        } else {
            echo ('Public Key Authentication Failed');
        }
        die();

can login and can upload files.