Best Practices when Creating Modules

When creating a ZF2 module, there are some best practices you should keep in mind.

Keep the init() and onBootstrap() methods lightweight

Be conservative with the actions you perform in the init() and onBootstrap() methods of your Module class. These methods are run for every page request, and should not perform anything heavy. As a rule of thumb, registering event listeners is an appropriate task to perform in these methods. Such lightweight tasks will generally not have a measurable impact on the performance of your application, even with many modules enabled. It is considered bad practice to utilize these methods for setting up or configuring instances of application resources such as a database connection, application logger, or mailer. Tasks such as these are better served through the ServiceManager capabilities.

Do not perform writes within a module

You should never code your module to perform or expect any writes within the module's directory. Once installed, the files within a module's directory should always match the distribution verbatim. Any user-provided configuration should be performed via overrides in the Application module or via application-level configuration files. Any other required filesystem writes should be performed in some writeable path that is outside of the module's directory.

There are two primary advantages to following this rule. First, any modules which attempt to write within themselves will not be compatible with phar packaging. Second, by keeping the module in sync with the upstream distribution, updates via mechanisms such as git will be simple and trouble-free. Of course, the Application module is a special exception to this rule, as there is typically no upstream distribution for this module, and it's unlikely you would want to run this package from within a phar archive.

Utilize a vendor prefix for module names

To avoid module naming conflicts, you are encouraged to prefix your module namespace with a vendor prefix. As an example, the developer tools module distributed by Zend is named "ZendDeveloperTools" instead of simply "DeveloperTools".

Utilize a module prefix for service names

If you define services in the top-level service manager, you are encouraged to prefix these services with the name of your module to avoid conflicts with other modules' services. For example, the database adapter used by MyModule should be called "MyModuleDbAdapter" rather than simply "DbAdapter." If you need to share a service with other modules, remember that the Service Manager "alias" feature can be used in a merged configuration to override factories defined by individual modules. Ideally, modules should define their own service dependencies, but aliases can be configured at the application level to ensure that common services in individual modules all refer to the same instance.