add_rewrite_rule – how to match exact whole word only?

Here’s the updated code with the explanation and last two lines added:

Updated Code with Last Two Lines

    add_action('query_vars', 'add_query_vars');
    function add_query_vars($vars) {
        $vars[] = 'verify'; // Add 'verify' as a query variable
        return $vars;
    }
    
    add_action('init', 'verify_add_rewrite_rule');
    function verify_add_rewrite_rule() {
        // Use ^verify/?$ to strictly match "verify" and ensure it ends there
        add_rewrite_rule('^verify/?$', 'index.php?verify=1&post_type=page', 'top');
    }
    
    add_filter('template_include', 'template_include_verify', 1000, 1);
    function template_include_verify($template) {
        if (get_query_var('verify')) {
            $new_template = get_template_directory() . '/verify.php';
            if (file_exists($new_template)) {
                $template = $new_template;
            }
        }
        return $template;
    }

Additional Notes:

Rewrite Rule Strict Matching: This ensures that only /verify/ (with or without a trailing slash) will match. No partial paths like /verifxx/ or /verify-xxx/ will be routed to your template.

Flush Rewrite Rules: After updating the code, navigate to Settings > Permalinks in WordPress and click “Save Changes” to flush the rewrite rules.