你好，为什么PHP使用PDO时读取没有记录的表会报错，如何处理？

Question

<?php//连接代码如下$servername = "localhost";$username = "root";$password = "pwdpdd!";$dbname = "color";$conn = null;try {$conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);//echo "连接成功";// 设置 PDO 错误模式为异常$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);$conn->exec("SET NAMES utf8");$conn->exec("SET character_set_server=utf8");}catch(PDOException $e){//echo $e->getMessage();}?><?php //以下为读取代码$stmt = null;try {$sql = "SELECT COUNT(*) AS total FROM colours";$stmt = $conn->prepare($sql);$stmt->execute();$stmt->setFetchMode(PDO::FETCH_ASSOC);while ($row = $stmt->fetch()) //如果表里没有记录，这句会报错{……}}catch(PDOException $e){//echo $e->getMessage();}?>

Answer 1

if(is_object($stmt ))先加一个这个判断，判断返回的变量是不是对象再决定如何调用！