Architecture

Celena is a hand-written PHP CMS with no third-party frameworks (no Laravel/Symfony) and no Composer dependencies in the core. All code is plain PHP 8.3+ with mandatory declare(strict_types=1) and strict typing.

If you're just starting out, read this page, then Project structure and Request lifecycle. To build extensions, move on to What is a plugin.

Entry points

File	Purpose
`index.php`	Site front — all public requests.
`admin.php`	Admin panel (thin loader, hands control to `Kernel`).
`install.php`	Self-deleting install wizard (after install an `install.lock` appears).
`bin/celena`	CLI: migrations, plugins, queue, cache.

Every request goes through the core Celena\Core\Kernel:

HTTP request → index.php → core/bootstrap.php → Kernel::boot()
  → Autoloader → Container → Config → services
  → Router::dispatch(Request) → Middleware → Controller → Response → send()

Layers

The code is split into four layers with a strict dependency direction:

Layer	Folder	Depends on
Core (domain-agnostic)	`core/`	only `core/*`
Built-in CMS modules	`modules/`	`core/*`
Plugins (extensions)	`plugins/`	`core/*`, optionally other plugins via manifest
Themes (appearance)	`templates/`	template engine tags only

The core knows nothing about news, shops or forms — it provides the tools (router, DB, template engine, hooks), while concrete functionality comes from modules and plugins.

Namespaces and autoloading

PSR-4 via core/Autoloader.php. Mappings:

Celena\Core\ → core/
Celena\Module\<Name>\ → modules/<Name>/
Celena\Plugin\<Slug>\ → plugins/<slug>/src/
Celena\Theme\<Slug>\ → templates/<slug>/

Rule: one class — one file. The file name matches the class name.

Contracts

declare(strict_types=1) everywhere; argument and return types are mandatory.
Any user input goes through Celena\Core\Security\Filter.
Any HTML output goes through e() (the escaping helper) or the template engine's auto-escaping.
Database access only via QueryBuilder or PDO::prepare. Concatenating values into SQL is forbidden.

Hooks (events)

Extensions talk to the core through a WordPress-style hook system — actions (side effects) and filters (value transformation):

use Celena\Core\Plugin\Hook;

Hook::action('news.published', $news);              // fire an action
Hook::on('news.published', fn($n) => /* ... */);    // subscribe

$title = Hook::filter('news.title', $news['title']); // apply filters
Hook::addFilter('news.title', fn($t) => trim($t));   // subscribe to a filter

Cache

Data cache is file-based by default (storage/cache/data); APCu/Redis optionally.
Templates are compiled to PHP and cached in storage/cache/tpl/{hash}.php. Invalidation is by source modification time (mtime) and manual.