2.2. Code Organization

Now that you know the different components of a symfony application, you're probably wondering how they are organized. Symfony organizes code in a project structure and puts the project files into a standard tree structure.

2.2.1. Project Structure: Applications, Modules, and Actions

In symfony, a project is a set of services and operations available under a given domain name, sharing the same object model.

Inside a project, the operations are grouped logically into applications. An application can normally run independently of the other applications of the same project. In most cases, a project will contain two applications: one for the front-office and one for the back-office, sharing the same database. But you can also have one project containing many mini-sites, with each site as a different application. Note that hyperlinks between applications must be in the absolute form.

Each application is a set of one or more modules. A module usually represents a page or a group of pages with a similar purpose. For example, you might have the modules home, articles, help, shoppingCart, account, and so on.

Modules hold actions, which represent the various actions that can be done in a module. For example, a shoppingCart module can have add, show, and update actions. Generally, actions can be described by a verb. Dealing with actions is almost like dealing with pages in a classic web application, although two actions can result in the same page (for instance, adding a comment to a post in a weblog will redisplay the post with the new comment).

Figure 2-3 shows a sample code organization for a weblog project, in a project/application/module/action structure. But be aware that the actual file tree structure of the project will differ from the setup shown in the figure.

Figure 2.3 Example of code organization

2.2.2. File Tree Structure

All web projects generally share the same types of contents, such as the following:

• A database, such as MySQL or PostgreSQL
• Static files (HTML, images, JavaScript files, style sheets, and so on)
• Files uploaded by the site users and administrators
• PHP classes and libraries
• Foreign libraries (third-party scripts)
• Batch files (scripts to be launched by a command line or via a cron table)
• Log files (traces written by the application and/or the server)
• Configuration files

Symfony provides a standard file tree structure to organize all these contents in a logical way, consistent with the architecture choices (MVC pattern and project/application/module grouping). This is the tree structure that is automatically created when initializing every project, application, or module. Of course, you can customize it completely, to reorganize the files and directories at your convenience or to match your client's requirements.

2.2.2.1. Root Tree Structure ###

These are the directories found at the root of a symfony project:

apps/
  frontend/
  backend/
cache/
config/
data/
  sql/
doc/
lib/
  model/
log/
plugins/
test/
  bootstrap/
  unit/
  functional/
web/
  css/
  images/
  js/
  uploads/

Table 2-1 describes the contents of these directories.

Table 2-1 - Root Directories

2.2.2.2. Application Tree Structure ###

The tree structure of all application directories is the same:

apps/
  [application name]/
    config/
    i18n/
    lib/
    modules/
    templates/
      layout.php

Table 2-2 describes the application subdirectories.

Table 2-2 - Application Subdirectories

The classes of an application are not able to access methods or attributes in other applications of the same project. Also note that hyperlinks between two applications of the same project must be in absolute form. You need to keep this last constraint in mind during initialization, when you choose how to divide your project into applications.

2.2.2.3. Module Tree Structure ###

Each application contains one or more modules. Each module has its own subdirectory in the modules directory, and the name of this directory is chosen during the setup.

This is the typical tree structure of a module:

apps/
  [application name]/
    modules/
      [module name]/
          actions/
            actions.class.php
          config/
          lib/
          templates/
            indexSuccess.php

Table 2-3 describes the module subdirectories.

Table 2-3 - Module Subdirectories

2.2.2.4. Web Tree Structure ###

There are very few constraints for the web directory, which is the directory of publicly accessible files. Following a few basic naming conventions will provide default behaviors and useful shortcuts in the templates. Here is an example of a web directory structure:

web/
  css/
  images/
  js/
  uploads/

Conventionally, the static files are distributed in the directories listed in Table 2-4.

Table 2-4 - Typical Web Subdirectories

| Directory | Description | ---------- | ----------- | css/ | Contains style sheets with a .css extension. | images/ | Contains images with a .jpg, .png, or .gif format. | js/ | Holds JavaScript files with a .js extension. | uploads/ | Can contain the files uploaded by the users. Even though the directory usually contains images, it is distinct from the images directory so that the synchronization of the development and production servers does not affect the uploaded images.