服务器-每次查询都得连接一次数据库，否则不继续执行的问题。

//连接数据库$pdo = new PDO("mysql:host=$db_host; dbname=$db_name", $db_username, $db_password); $pdo->query('SET NAMES utf8');//导入活动信息$sql = "SELECT * FROM activity WHERE a_id = '$activity_id'";$rs = $pdo->query($sql);while($row = $rs->fetch()){    $activity_uno=$row['u_no'];    $activity_name=$row['a_name'];}//导入用户信息$sql = "SELECT * FROM user WHERE No = '$activity_uno'";$rs = $pdo->query($sql);while($row = $rs->fetch()){    $activity_usernick=$row['Nickname'];    $activity_uservtype=$row['vtype'];    $activity_userverify=$row['verify'];}

在本机上（WAMP环境）这样写的代码，运行结果是正常的，一次连接就可以多次查询。但是传到服务器上（LAMP），每次查询前都要连接一次数据库，否则就不会继续查询。
在服务器上改成这样才能正常：

 //连接数据库$pdo = new PDO("mysql:host=$db_host; dbname=$db_name", $db_username, $db_password); $pdo->query('SET NAMES utf8');//导入活动信息$sql = "SELECT * FROM activity WHERE a_id = '$activity_id'";$rs = $pdo->query($sql);while($row = $rs->fetch()){    $activity_uno=$row['u_no'];    $activity_name=$row['a_name'];}//连接数据库$pdo = new PDO("mysql:host=$db_host; dbname=$db_name", $db_username, $db_password); $pdo->query('SET NAMES utf8');//导入用户信息$sql = "SELECT * FROM user WHERE No = '$activity_uno'";$rs = $pdo->query($sql);while($row = $rs->fetch()){    $activity_usernick=$row['Nickname'];    $activity_uservtype=$row['vtype'];    $activity_userverify=$row['verify'];}

请问问题出在哪里？如何才能像本机上测试那样一次连接多次查询？