Restrict a category to specific user role

<?php
/**
This snippet restricts a category to a specific user role. You can modify the $restricted_role and $restricted_category_slug accordingly.

For installation instructions, see our documentation site: http://wp-events-plugin.com/tutorials/how-to-safely-add-php-code-to-wordpress/
*/
function restrict_event_categories_by_user_role($search_args) {
    // Get the current user
    $user = wp_get_current_user();

    // Define the role and category to restrict
    $restricted_role = 'contributor';
    $restricted_category_slug = 'contributors-only';

    // Check if the user does not have the restricted role
    if (!in_array($restricted_role, $user->roles)) {
        // Get the category term by slug
        $restricted_category = get_term_by('slug', $restricted_category_slug, 'event-categories');

        if ($restricted_category) {
            $restricted_category_id = '-' . $restricted_category->term_id; // Use negative ID to exclude

            // Ensure category is an array
            if (!is_array($search_args['category'])) {
                // If it's not an array, split it by commas or initialize it as an array if empty
                $search_args['category'] = !empty($search_args['category']) ? explode(',', $search_args['category']) : array();
            }

            // Check if the category is not already in the array (either included or excluded)
            if (!in_array($restricted_category_id, $search_args['category']) && !in_array(ltrim($restricted_category_id, '-'), $search_args['category'])) {
                // Add the restricted category to the array to exclude it
                $search_args['category'][] = $restricted_category_id;
            }

            // Convert the array back to a string if needed
            $search_args['category'] = implode(',', $search_args['category']);
        }
    }

    return $search_args;
}
add_filter('em_events_get_default_search', 'restrict_event_categories_by_user_role');