private function taxonomy_select_field($field = array()) {
    if ( isset( $field['label'] ) ) {
        $this->label();
    }

    $this->output .= '<div class="ap-form-fields-in">';

    $taxonomies = wp_dropdown_categories( array(
                'taxonomy'     => $field['taxonomy'],
                'orderby'      => @$field['orderby'],
                'hide_empty'   => 0,
                'hierarchical' => 1,
                'selected'     => @$field['value'],
                'name'         => @$field['name'],
                'class'        => 'ap-form-control',
                'id'           => @$field['name'],
                'echo'         => false
    ) );

    $this->output .= $taxonomies;

    $this->error_messages();

    if ( ! $this->field['show_desc_tip'] ) {
        $this->desc();
    }

    $this->output .= '</div>';
}