pdo为何不用用户名和密码可以操作成功

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$dsn = "mysql:host=localhost;dbname=test";  <br />
<br />
try{<br />
    $pdo = new PDO($dsn);<br />
    echo "连接成功";<br />
    }catch(PDOException $e){<br />
    echo "连接失败".$e->getMessage();<br />
}<br />
<br />
<br />
try{<br />
	  $pdo->beginTransaction();<br />
	  $goodprice = 5;<br />
	  $id_out = 15;<br />
	  $id_in =16;<br />
	  $sql1 ="update price set goodprice【本文来自鸿网互联 (http://www.68idc.cn)】 = goodprice -{$goodprice} where id ={$id_out}";<br />
	  $sql2 ="update price set goodprice = goodprice +{$goodprice} where id ={$id_in}";    	 <br />
	  if(!$affectd_rows =$pdo->exec($sql1)){<br />
	  	  throw new PDOException("{$id_out}转出失败");<br />
	  }<br />
	  if(!$affectd_rows =$pdo->exec($sql2)){<br />
	  	  throw new PDOException("{$id_in}转入失败");<br />
	  }<br />
	  $pdo->commit();<br />
	   echo "提交成功";<br />
}catch(PDOException $e){<br />
	  echo $e->getMessage();<br />
         $pdo->rollback();<br />
} <br />