PHP复习第二天PDO

<?php
header("Context-Type:text/html;charset=utf-8");
$dbms="mysql";
$dbName="zhangbuxin";
$user="root";
$pwd="";
$host="localhost";
$dsn="$dbms:host=$host;$dbName=$dbName";
try{
$pdo=new PDO($dsn,$user,$pwd);
echo 'PDO 链接MYSQL成功!<br/>';
if($pdo){
$result = $pdo -> prepare("select * from zy_role");
$result->execute(); 
while($row = $result -> fetchAll(PDO::FETCH_ASSOC)){ 
echo $row['id'];
echo $row['name'];
echo "<br/>";
}

}else{
echo 'PDO 链接MYSQL失败!<br/>';
}
}catch(PDOException $e){
echo $e->getMessage().'<br/>';

}

?>