php使用PDO下exec()函数查询执行后受影响行数的方

try{
 $conn=new PDO("mysql:host=$servername;dbname=$dbname", $username,$password);
 $conn->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
 $sql="INSERT INTO `hello`(`firstname`,`lastname`,`email`)values('ye','xianming','1150416034@qq.'),
  ('xiao','hua','xiaohua@163.')";
 $conn->exec($sql);
 echo "Insert record suess";
}catch(PDOException $e){
  echo "Error:".$e->getMessage();
}

try{
 $conn=new PDO("mysql:host=$servername;dbname=$dbname",$username,$password);
 $conn->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
 $sql="delete from hello where id=61";
 $conn->exec($sql);
 echo "delete record suess";
}catch(PDOException $e){
  echo "Error".$e->getMessage();
}

try{
 $conn=new PDO("mysql:host=$servername;dbname=$dbname",$username,$password);
 $conn->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
 $sql="UPDATE hello SET firstname='xiao',lastname='ming' WHERE id='62'";
 $conn->exec($sql);
 echo "update record suess";
}catch(PDOException $e){
 echo "Error".$e->getMessage();
}

try{
 $conn=new PDO("mysql:host=$servername;dbname=$dbname",$username,$password);
 $conn->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
 $sql="select  from hello";
 $query=$conn->exec($sql);
 for($i=0;$i<count($query);$i++){
  print_r($query);
 }
  echo "select record suess";
}catch(PDOException $e){
  echo "Error".$e->getMessage();
}