我创建了两个下拉列表，每个下拉列表一个category & tag 并成功筛选帖子。

之后，我创建了一个自定义分类法cat 并尝试在所有三个下拉列表之间过滤帖子。但用于分类的下拉列表cat 不工作。

<form action="<?php bloginfo(\'url\'); ?>" method="get">                  
<?php
// I use custom taxonomy  "Cat"
    if( $terms = get_terms( \'cat\', \'orderby=name\' ) ) :
        echo \'<select name="cat_name"> <option value="">Cat</option>\';
        foreach ( $terms as $term ) :
            echo \'<option value="\' . $term->name . \'">\' . $term->name . \'</option>\';
        endforeach;
        echo \'</select>\';
    endif;
// I use default  "Categories"
    if( $terms = get_terms( \'category\', \'orderby=name\' ) ) : 
        echo \'<select name="category_name"> <option value="">Categories</option>\';
        foreach ( $terms as $term ) :
            echo \'<option value="\' . $term->name . \'">\' . $term->name . \'</option>\';
        endforeach;
        echo \'</select>\';
    endif;
// I use default  "Tag"
    if( $terms = get_terms( \'post_tag\', \'orderby=name\' ) ) :
        echo \'<select name="tag"><option value="">Tags</option>\';
        foreach ( $terms as $term ) :
            echo \'<option value="\' . $term->name . \'">\' . $term->name . \'</option>\';
        endforeach;
        echo \'</select>\';
    endif;
?>
<input type="submit" name="submit" value="filter" />
</form>

What I missing or any suggestions to make all three dropdown working?

function custom_taxonomies() {
    $labels = array(
        \'name\' => \'Cat\',
        \'singular_name\' => \'Cat\',
        \'menu_name\' => \'Cat\'
    );
    $args = array(
        \'hierarchical\' => true,
        \'labels\' => $labels,
        \'show_ui\' => true,
        \'show_admin_column\' => true,
        \'query_var\' => true,
        \'rewrite\' => array( \'slug\' => \'cat\' )
    );
    register_taxonomy(\'cat\', array(\'post\'), $args); 
}
add_action( \'init\' , \'custom_taxonomies\' );