# Functionality

The app/ directory contains all of the theme functionality. Since Sage is a starter theme, it’s okay for you to modify files within app/ to meet the needs of the site you’re building.

The PHP code in Sage is namespaced, so make sure to use namespaced functions and classes.

  • app/setup.php – Enqueue stylesheets and scripts, register support for theme features with add_theme_support, register navigation menus and sidebars. See Theme Configuration and Setup.

  • app/admin.php – Placeholder code for the WordPress theme customizer. You can also use this file for anything related to the WordPress admin.

  • app/filters.php – Add WordPress filters in this file. Filters included by default:

    • body_class – add <body> classes
    • excerpt_more – add "… Continued" to excerpts
    • template_include – enable the theme wrapper
    • Various filters for the Blade implementation
  • app/helpers.php – Helper functions used throughout the theme:

    • asset_path – used when enqueueing theme assets to provide the correct versioned asset filenames
    • display_sidebar – used to control displaying the sidebar
    • title – used to return page titles