1.在学习php时用PDO模式连接数据库，查询数据时，在调用fetch方法时出现错误：Fatal error: Call to a member function fetch() on a non-object
2.代码

//PDO连接数据库方式
     try{
         $db_conn = new PDO('mysql:host = localhost;dbname = test','root','123456');
         echo "连接成功！";
     }
     catch(PDOException $e){
         echo "Could not connect to datebase";
     }

//从表中选取数据
     $stmt = $db_conn->query('SELECT * FROM user');
     var_dump($stmt);
//显示结果
     while ($row = $stmt->fetch()) {
         echo $row['name'].$row['number'].$row['class'];
     }

3.错误结果

4.数据库