php登录会话未登录但重复相同的页面

Question

session_start();
      include_once 'oesdb.php';

 //redirect to registration page
      if(isset($_REQUEST['register']))
      {
            header('Location: register.php');
      }
      else if($_REQUEST['stdsubmit'])
      {

 //Perform Authentication
          $result=executeQuery("select *,DECODE(stdpassword,'oespass') as std from student where stdname='".htmlspecialchars($_REQUEST['name'],ENT_QUOTES)."' and stdpassword=ENCODE('".htmlspecialchars($_REQUEST['password'],ENT_QUOTES)."','oespass')");
          if(mysql_num_rows($result)>0)
          {

              $r=mysql_fetch_array($result);
              if(strcmp(htmlspecialchars_decode($r['std'],ENT_QUOTES),(htmlspecialchars($_REQUEST['password'],ENT_QUOTES)))==0)
              {
                  $_SESSION['stdname']=htmlspecialchars_decode($r['stdname'],ENT_QUOTES);
                  $_SESSION['stdid']=$r['stdid'];
                  unset($_GLOBALS['message']);
                  header('Location: stdwelcome.php');
              }else
          {
              $_GLOBALS['message']="Check Your user name and Password.";
          }

          }
          else
          {
              $_GLOBALS['message']="Check Your user name and Password.";
          }
          closedb();

这是我的index.php的一部分。它成功注册，当我检查服务器上的数据库时，看到新用户，但是当我尝试登录时，它通过不显示无效密码接受，但它拒绝登录。我想它不会创建登录所需的会话。