为什么PHP会抛出这个错误？

Question

试图允许php使用相同的变量查询来拉'代码'和'前缀'字段。

错误：'code'

<script type="text/javascript"> 
    $(document).ready(function() { 
     $("#ProfFields,#courseFields").hide(); 
     $("input:radio[name='addType']").click(function(){ 
      var profFields = ($(this).val()=="Professor"); 
      $("#ProfFields").toggle(profFields); 
      $("#courseFields").toggle(!profFields); 
    }); 
    }); 
    </script> 
    <?php 
    require_once('inc/dbc1.php'); 
    $pdo = new PDO('mysql:host=ureviewdu.db.6511651.hostedresource.com;dbname=ureviewdu', $username, $password); 
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
    $sth = $pdo->prepare(' 
     SELECT name 
     FROM Department 
     ;'); 
    $sth->execute(array()); 

    $pdo2 = new PDO('mysql:host=####;dbname=###', $username, $password); 
    $pdo2->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
    $sth2 = $pdo2->prepare(' 
     SELECT prefix, code FROM Course 
     ;'); 
    $sth2->execute(array()); 
    ?> 
    <div id="popup_name" class="popup_block"> 
     <h2 style="padding:0; margin:0;">Add a:</h2><br> 
     <form action="inc/add_p_c_validate.php" method="post" id="addition"> 
      Professor<input type="radio" name="addType" value="Professor" /> 
      &nbsp;&nbsp;Course<input type="radio" name="addType" value="Course" /> 

      <div id="courseFields"> 

        Course[Prefix]: <select name="cPrefix" id="cPrefix" style="width:150px;" /> 
        <?php while($row2 = $sth2->fetch(PDO::FETCH_ASSOC)) {echo "<option>".$row2['prefix']." "."</option><br>";} ?> </select> 

        Course[Code]: <select name="cCode" id="cCode" style="width:150px;" /> 
        <?php while($row2 = $sth2->fetch(PDO::FETCH_ASSOC)) {echo "<option>".$row2['code']." "."</option>";} ?></select> 

       Department: <select name="deptName" id="deptName" style="width:350px;"> 
        <?php while($row = $sth->fetch(PDO::FETCH_ASSOC)) {echo "<option>".$row['name']." "."</option>";} ?></select> 
       Email: <input type="text" name="email" class="l" /> 
      </div><!--/courseFields--> 
      <div id="ProfFields"> 
      <br>First Name: <input type="text" name="name" style="width:385px;" /><br> 
      <br>Last Name: <input type="text" name="name" style="width:385px;" /><br> 
       Department: <select name="deptName" id="deptName" style="width:350px;"> 
      </div><!--/ProfFields--> 
      <input type="submit" name="submit" /> 
     </form> 
    </div><!--popup_name-->