Joomla！ 通过调用数据库填充注册表上的列表框

Question

Thanks in advance for your help...

I have modified the registration.xml file and other files as necessary to add additional forms to my registration form on mhy Joomla! site. The fields are currently all text boxes and I want to create list boxes for items like state. I don't want to type in the options and values, but rather pull from a table on the database.

This code in my registration.xml file works:

<field name="statelist2" type="list" 
default=""
label="COM_USERS_REGISTER_STATE_LABEL"
description="COM_USERS_REGISTER_STATE_DESC"
message="COM_USERS_REGISTER_STATE_MESSAGE">
<option value="CT">CT</option>
<option value="MA">MA</option>
</field>

This code in my registration.xml file does NOT work and I tried removing the call to the DB to just get the page to load with some php:

<field name="statelist" 
type="list"
default=""
label="COM_USERS_REGISTER_STATE_LABEL"
description="COM_USERS_REGISTER_STATE_DESC"
message="COM_USERS_REGISTER_STATE_MESSAGE">
<?php
$x = "CT";
$z = "NY";
echo "<option value='" . $x. "'>" . $x . "</option>"; 
echo "<option value='" . $z. "'>" . $z . "</option>"; 
?>
</field>

My question(s): 1) Where do I have to put the code (in what file) in order to either create the list box or populate it with potential values?

2) In order to take advantage of the existing Joomla! framework, I see in the registration.php files some functions for loadFormData and getData - can I put code in there to populate items in the registration form after it's been rendered? I was thinking something like this, but not sure.

<?php 
    //init Joomla Framework 
    define( '_JEXEC', 1 ); 
    define( 'DS', DIRECTORY_SEPARATOR ); 
    define( 'JPATH_BASE', realpath(dirname(__FILE__).DS.'..' )); 


    require_once ( JPATH_BASE .DS.'includes'.DS.'defines.php' ); 
    require_once ( JPATH_BASE .DS.'includes'.DS.'framework.php' ); 

    $mainframe = JFactory::getApplication('site'); 

    //DBQuery 
    $database =& JFactory::getDBO(); 
    $query = "SELECT * FROM #__tbl_State;"; 

$database->setQuery($query); 
    //$result = $database->query();
$items = ($items = $db->loadObjectList())?$items:array(); 
    //print_r($result); 
?> 

Answer 1

<field
        name="STUDENT_COURSE"
        type="sql"
        multiple="false"
        size="1"
        label="Interested In Course"
        description="COM_HELLOWORLD_FORM_DESC_UPDHELLOWORLD_GREETING"
        query="select Course_Id, Course_Name from student_course"
        key_field="Course_Id"
        value_field="Course_Name"
        default="0"
required="true"
        >
     <option value="">Please Select Course</option>
</field>

Answer 2

Wow, it looks to me like you are making hard work of it.

Unless I am missing something, and I often do, you could simply use the right tool for the job ;) http://docs.joomla.org/SQL_form_field_type

Failing that you might find another field type that will work for you. http://docs.joomla.org/Standard_form_field_types