度数据库报错-用php逐条读取mysql中的数据报错为什么？？

';            echo $b["1"].'
';        }?>

为什么下面会报错？？

Notice: Undefined offset: 1 in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\project\brief.php on line 25Do you think it will Notice: Undefined offset: 1 in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\project\brief.php on line 25Do you think itNotice: Undefined offset: 1 in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\project\brief.php on line 25