How to get selected taxonomy or category ID if using custom walker?

Question

I'm building a taxonomy->child taxonomy dropdowns where the child will only be active if the parent is selected. Everything works great, except that I'm using wp_dropdown_categories for the parent and the value that I get is an ID of the selected item instead of slug or name.

For that reason I'm using a custom walker to get the name and it works great, my issue is that because I'm using this walker now, I cannot get the ID of the selected parent to activate the child dropdown.

  wp_dropdown_categories(array(
'show_count' => 1,
'selected' => 0,
'hierarchical' => 1,
'depth' => 1,
'hide_empty' => 0,
'tab_index' => $tabindex,
'class' => 'gt-select',
'show_option_none' => 'Select Product',
'name' => 'cat',
'id' => 'my-product',
'taxonomy' => 'products',
'walker' => new Walker_CategoryDropdown_Custom(),
));

The child taxonomy code is:

$cat_id = sanitize_text_field($_POST['cat']);
$cat_query = "child_of={$cat_id}&hide_empty=0&taxonomy=products";
$categories = get_categories($cat_query);
$options = '<option value="-1">Select Color</option>';
foreach ($categories as $cat) {
  $name = $cat->name;
  $value = $cat->term_id;
  $label = "{$cat->cat_name} ({$cat->category_count})";
  $options .= "<option value=\"{$name}\" data-value=\"{$value}\">{$label}</option>";
}

$return = array(
  'options' => $options,
);

The issue with using the Custom Walker is that now instead of getting the id here:

$cat_id = sanitize_text_field($_POST['cat']);

I'm getting the parent category name or slug, if I take the walker out everything works great but wp_dropdown_categories() will insert a new record with the ID number in the categories instead of updating the existing one.

I'm adding the Custom walker here just for reference:

class Walker_CategoryDropdown_Custom extends Walker_CategoryDropdown
    {
        function start_el(&$output , $category , $depth , $args)
        {
            $pad = str_repeat(' ' , $depth * 3);$cat_name = apply_filters('list_cats' , $category->name , $category);
            $output .= "\t<option class=\"level-$depth\" value=\"" . $category->name . "\" data-value=\"" . $category->term_id . "\"";
            if ( $category->term_id == $args[ 'selected' ] ) $output .= ' selected="selected"';
            $output .= '>';
            $output .= $pad . $cat_name;
            if ( $args[ 'show_count' ] ) $output .= '  (' . $category->count . ')';
            if ( array_key_exists('show_last_update', $args) && $args[ 'show_last_update' ] ) {
                $format = 'Y-m-d';
                $output .= '  ' . gmdate($format , $category->last_update_timestamp);
            }
            $output .= "</option>\n";

        }

    }

The value of the output is:

value=\"" . $category->name . "\" 

and the parent category works great updating itself in the database but the child category dropdown will not populate.

If I change this in the walker to:

value=\"" . $category->term_id . "\" 

The child will populate but the parent category will not update and it will insert itself as a new record with the ID number as the label.

Basically I need to find a way to get the selected category ID from wp_dropdown_categories() and pass that here:

$cat_id = sanitize_text_field($_POST['cat']);

Answer 1

May be easier to just work with it, than against it...

Instead of:

$cat_id = sanitize_text_field($_POST['cat']);

Try:

$cat_name = sanitize_text_field( $_POST['cat'] );
$cat = get_term_by( 'name', $cat_name, 'category' );
$cat_id = $cat->term_id;