php入门pdo的使用－－增加数据，查询数据

<?php
    try{
        //$dsn 数据库驱动，
        $dsn = "mysql:dbname=classphp;host=127.0.0.1";
        $name = "root";
        $pwd = "";
        $pdo = new PDO($dsn,$name,$pwd);
        //设置错误处理模式，推荐为异常处理模式
        $pdo -> setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
        echo $pdo -> getAttribute(PDO::ATTR_ERRMODE);
        $username = "jixue";
        $pwd = md5(12345);
        $email = "18868831752@163.com";
        $sql = "INSERT INTO PERSON(username,pwd,email) VALUE('{$username}','{$pwd}','{$email}')";
        //exec只执行有影响行数的语句（通常指增，删，改） 
        $affected = $pdo -> exec($sql);
        //query执行有结果集的语句 (通常指查询)
        $sql = "SELECT * FROM PERSON";
        $stmt = $pdo -> query($sql);
        var_dump($stmt);
        echo "<hr/>";
        var_dump($affected);
        echo "<hr/>";
        foreach ($stmt as $key ) {
            echo "{$key['id']}-{$key['username']}-{$key['pwd']}-{$key['email']}-<br/>";
        }
        // var_dump($pdo);
    }
    catch(PDOException $e){
        echo $e -> getMessage();
        echo $e -> getFile();
        echo $e -> getLine();
        echo $e -> getCode();

    }
?>

执行后页面显示：

上面代码打印输出