我在一个WP站点中有3个分层（类）自定义分类，books, characters 和writers. 我想在站点的侧栏中为每个术语创建一个动态填充的下拉菜单，以便在任何下拉菜单中选择术语时，站点自动加载相应的存档。

使用所述方法here 我只能在一种分类法上使用它。我一加上更多，就发现只有最后一个有效。

这是我到目前为止的情况。显然，我需要找到一种方法，使函数的后续实例不会超过早期实例。我认为更改ID和函数名可以做到这一点，但显然没有那么简单。

<?php
    $writers = get_categories(\'taxonomy=writers\');
    $select = "<select name=\'writers\' id=\'writers\' class=\'postform\'>n";
    $select.= "<option value=\'-1\'>Writers</option>n";
    foreach($writers as $writer){
        if($writer->count > 0){
            $select.= "<option value=\'".$writer->slug."\'>".$writer->name."</option>";
        }
    }
    $select.= "</select>";
    echo $select;
?>
<?php
    $characters = get_categories(\'taxonomy=characters\');
    $select = "<select name=\'characters\' id=\'characters\' class=\'postform\'>n";
    $select.= "<option value=\'-1\'>Characters</option>n";
    foreach($characters as $character){
        if($character->count > 0){
            $select.= "<option value=\'".$character->slug."\'>".$character->name."</option>";
        }
    }
    $select.= "</select>";
    echo $select;
?>
<?php
    $books = get_categories(\'taxonomy=books\');
    $select = "<select name=\'books\' id=\'books\' class=\'postform\'>n";
    $select.= "<option value=\'-1\'>Books</option>n";
    foreach($books as $book){
        if($book->count > 0){
            $select.= "<option value=\'".$book->slug."\'>".$book->name."</option>";
        }
    }
    $select.= "</select>";
    echo $select;
?>

<script>
    var dropdown = document.getElementById("writers");
    function onWriterChange() {
        if ( dropdown.options[dropdown.selectedIndex].value != -1 ) {
        location.href = "<?php echo home_url();?>/writer/"+dropdown.options[dropdown.selectedIndex].value+"/";
        }
    }
    dropdown.onchange = onWriterChange;

    var dropdown = document.getElementById("characters");
    function onCharacterChange() {
        if ( dropdown.options[dropdown.selectedIndex].value != -1 ) {
        location.href = "<?php echo home_url();?>/character/"+dropdown.options[dropdown.selectedIndex].value+"/";
        }
    }
    dropdown.onchange = onCharacterChange;

    var dropdown = document.getElementById("books");
    function onBookChange() {
        if ( dropdown.options[dropdown.selectedIndex].value != -1 ) {
        location.href = "<?php echo home_url();?>/book/"+dropdown.options[dropdown.selectedIndex].value+"/";
        }
    }
    dropdown.onchange = onBookChange;
</script>