2
$ele = new XoopsFormSelect($caption, $name, $value=null, $size=1, $multiple=false);
$ele->addOption($value,$name);
/* or */
$options = array(0=>'Opt1',1=>'opt2');
$ele->addOptionArray($options);
$this->addElement($ele);
unset($ele); //only need this if you are going to reuse $ele
TIP
Although XOOPS is not well documented, you do have access to the source code. Get yourself familiar with the 'class' directory and its contents, in your XOOPS installation. For forms, you'll find all the declaration in the class/xoopsform directory