Application is expected to have following structure:
document root
│
├── app  . . . . . . . . . . .  Application specific files
│   ├── block  . . . . . . . .  Blocks
│   ├── class  . . . . . . . .  Classes within application namespace
│   ├── style  . . . . . . . .  CSS and related picture
│   ├── template . . . . . . .  Templates (subdir for each output type)
│   │   ├── css
│   │   ├── html5
│   │   ├── json
│   │   └── latex
│   └── test . . . . . . . . .  Tests
│
├── core . . . . . . . . . . .  Framework core (this package)
│   ├── bin  . . . . . . . . .  Helper scripts and binaries
│   ├── block  . . . . . . . .  Blocks
│   ├── class  . . . . . . . .  Core framework implementation
│   ├── doc  . . . . . . . . .  Documentation
│   │   └── doxygen  . . . . .  Generated documentation (by Doxygen)
│   ├── examples   . . . . . .  Example files and configuration templates
│   ├── style  . . . . . . . .  Elementary styles and related images
│   ├── template . . . . . . .  Core template (subdir for each output type)
│   │   ├── css
│   │   ├── html5
│   │   ├── json
│   │   └── latex
│   └── test . . . . . . . . .  Tests (using PHPT)
│
├── data   . . . . . . . . . .  Application data (writable by webserver)
│
├── lib  . . . . . . . . . . .  3rd party libraries (managed by Composer)
│   ├── cascade
│   │   └── composer-plugin
│   ├── composer   . . . . . .  Composer's autoloader
│   :
│
├── plugin   . . . . . . . . .  Plugins (managed by Composer)
│   ├── plugin_name  . . . . .  Each plugin has its own subdirectory
│   │   ├── block               with the same structure as core and app.
│   │   ├── class
│   │   ├── style
│   │   ├── template
│   │   └── test
│   :
│
└── var  . . . . . . . . . . .  Variable data, caches, temporary files (writable by webserver)
    ├── graphviz   . . . . . .  Diagrams rendered by Graphviz
    :