嘗試從名稱空間加載類時，是否忘記了另一個名稱空間的「use」語句？

Question

我在我的代碼中使用了一個Cassandra類，並且此錯誤總是顯示出來「嘗試從命名空間加載類時，是否忘記了」使用「其他命名空間的語句？這裏是我的代碼

DefaultController

<?php 

namespace Acme\SampleBundle\Controller; 

use Symfony\Bundle\FrameworkBundle\Controller\Controller; 
use Cassandra; 

class DefaultController extends Controller 
{ 
public function indexAction() 
{ 
    $con = new Cassandra\Timestamp(); 

    echo $con; 
} 
} 

Timestap.php

<?php 

/** 
* Copyright 2015-2016 DataStax, Inc. 
* 
* Licensed under the Apache License, Version 2.0 (the "License"); 
* you may not use this file except in compliance with the License. 
* You may obtain a copy of the License at 
* 
* http://www.apache.org/licenses/LICENSE-2.0 
* 
* Unless required by applicable law or agreed to in writing, software 
* distributed under the License is distributed on an "AS IS" BASIS, 
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
* See the License for the specific language governing permissions and 
* limitations under the License. 
*/ 

namespace Cassandra; 

/** 
* A PHP representation of the CQL `timestamp` datatype 
*/ 
final class Timestamp implements Value 
{ 
/** 
* Creates a new timestamp from either unix timestamp and microseconds or 
* from the current time by default. 
* 
* @param int $time Unix timestamp 
* @param int $usec Microseconds 
*/ 
public function __construct($time = null, $usec = null) {} 

/** 
* The type of this timestamp. 
* 
* @return Type 
*/ 
public function type() {} 

/** 
* Unix timestamp. 
* 
* @return int seconds 
* @see time 
*/ 
public function time() {} 

/** 
* Microtime from this timestamp 
* 
* @param bool $get_as_float Whether to get this value as float 
* 
* @return float|string Float or string representation 
* @see microtime 
*/ 
public function microtime($get_as_float = false) {} 

/** 
* Converts current timestamp to PHP DateTime. 
* 
* @return \DateTime PHP representation 
*/ 
public function toDateTime() {} 

/** 
* Returns a string representation of this timestamp. 
* 
* @return string timestamp 
*/ 
public function __toString() {} 
} 

我不知道什麼是錯在我的代碼，我使用的卡桑德拉和symfony的新手

Answer 1

你是否在配置文件中定義了密鑰空間？

你可以找到一個例子中，我沒有使用任何密鑰空間現在here