Rewrite the HTML output of radio buttons into a Bootstrap dropdown

facetwp.php

<?php

// Adjust FacetWP "Radio" HTML output to be friendlier with our theme
add_filter('facetwp_facet_html', function ($output, $params) {
    
    // Check that this facet is a "radio" type facet before proceeding.
    if ('radio' == $params['facet']['type']) {
        
        // Initialize our variables
        $output = '';
        $buttons = '';
        $selected_label = '';
        
        // Get the selected values for the facet
        $selected_values = (array) $params['selected_values'];
        
        // Get all the values for the facet
        $values = (array) $params['values'];
        
        // Loop through the values and create our dropdown items, marking them as "checked" or "disabled" as needed 
        foreach ($values as $key => $result) {
            
            // Write the markup for each button, this example comments out the "counter" span
            $buttons .= sprintf(
                '<button class="dropdown-item facetwp-radio %s" data-value="%s">%s</button>',
                in_array($result['facet_value'], $selected_values) ? ' checked active' : '', // If this item is selected, add the "checked" and "active" classes
                $selected .= (0 == $result['counter'] && '' == $selected) ? ' disabled' : '', // If this item is disabled, add the "disabled" class
                $selected_label .= in_array($result['facet_value'], $selected_values) ? esc_html($result['facet_display_value']) : '', // Get the label of the selected item so we can use it for the dropdown trigger button text
            );
        }
    }
    
    // Write the markup for the dropdown
    $output = sprintf(
        '<div class="dropdown">
           <button type="button" class="btn btn-light btn-block dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
             %s
           </button>
           <div class="dropdown-menu w-100">
             %s
           </div> <!-- /.dropdown-menu -->
         </div> <!-- /.btn-dropdown -->',
        ($selected_label) ? $selected_label : $params['facet']['label_any'], // Set the selected label, or set it to the default
        $buttons,
       );
    
    // Return the whole darn thing
    return $output;
}, 10, 2);