为什么 $pdo->exec($sql)总是返回false

Question

//创建pdo对象$pdo = new PDO($dsn,$username,$password);var_dump($pdo);//输出为object(PDO)#1 (0) { } //执行插入语句 $sql = "INSERT INTO text VALUES (NULL ,'名2' ,25 ,32222 )";$records = $pdo->exec($sql);var_dump($records);