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How to expose new API methods in the HTTP Reporting API – Introducing the Piwik Platform

This is the next post of our blog series where we introduce the capabilities of the Piwik platform (our previous post was How to write UI tests for your plugin). This time you’ll learn how to extend our Reporting API. For this tutorial you will need to have basic knowledge of PHP.

What is Piwik’s Reporting API?

It allows third party applications to access analytics data and manipulate miscellaneous data (such as users or websites) through HTTP requests.

What is it good for?

The Reporting API is used by the Piwik UI to render reports, to manage users, and more. If you want to add a feature to the Piwik UI, you might have to expose a method in the API to access this data. As the API is called via HTTP it allows you to fetch or manipulate any Piwik related data from anywhere. In these exposed API methods you can do pretty much anything you want, for example:

  • Enhance existing reports with additional data
  • Filter existing reports based on custom rules
  • Access the database and generate custom reports
  • Persist and read any data
  • Request server information

Getting started

In this series of posts, we assume that you have already set up your development environment. If not, visit the Piwik Developer Zone where you’ll find the tutorial Setting up Piwik.

To summarize the things you have to do to get setup:

  • Install Piwik (for instance via git).
  • Activate the developer mode: ./console development:enable.
  • Generate a plugin: ./console generate:plugin --name="MyApiPlugin". There should now be a folder plugins/MyApiPlugin.
  • And activate the created plugin: ./console plugin:activate "MyApiPlugin"

Let’s start creating an API

We start by using the Piwik Console to create a new API:

./console generate:api

The command will ask you to enter the name of the plugin the created API should belong to. I will simply use the above chosen plugin name “MyApiPlugin”. There should now be a file plugins/MyApiPlugin/API.php which contains already an example to get you started easily:

class API extends PiwikPluginAPI
{ public function getAnswerToLife($truth = true) { if ($truth) { return 42; } return 24; } public function getExampleReport($idSite, $period, $date, $wonderful = false) { $table = DataTable::makeFromSimpleArray(array( array('label' => 'My Label 1', 'nb_visits' => '1'), array('label' => 'My Label 2', 'nb_visits' => '5'), )); return $table; }
}

Any public method in that file will be available via the Reporting API. For example the method getAnswerToLife can be called via this URL: index.php?module=API&method=MyApiPlugin.getAnswerToLife. The URL parameter method is a combination of your plugin name and the method name within this class.

Passing parameters to your method

Both example methods define some parameters. To pass any value to a parameter of your method simply specify them by name in the URL. For example ...&method=MyApiPlugin.getExampleReport&idSite=1&period=week&date=today&wonderful=1 to pass values to the parameters of the method getExampleReport.

Returning a value

In an API method you can return any boolean, number, string or array value. A resource or an object cannot be returned unless it implements the DataTableInterface such as DataTable (the primary data structure used to store analytics data in Piwik), DataTableMap (stores a set of DataTables) and DataTableSimple (a DataTable where every row has two columns: label and value).

Did you know? You can choose the response format of your API request by appending a parameter &format=JSON|XML|CSV|... to the URL. Check out the Reporting API Reference for more information.

Best practices

Check user permissions

Do not forget to check whether a user actually has permissions to access data or to perform an action. If you’re not familiar with Piwik’s permissions and how to check them read our User Permission guide.

Keep API methods small

At Piwik we aim to write clean code. Therefore, we recommend to keep API methods small (separation of concerns). An API pretty much acts like a Controller:

public function createLdapUser($idSite, $login, $password)
{ Piwik::checkUserHasAdminAccess($idSite); $this->checkLogin($login); $this->checkPassword($password); $myModel = new LdapModel(); $success = $myModel->createUser($idSite, $login, $password); return $success;
}

This is not only easy to read, it will also allow you to create simple tests for LdapModel (without having to bootstrap the whole Piwik layer) and you will be able to reuse it in other places if needed.

Calling APIs of other plugins

For example if you want to fetch an existing report from another plugin, say a list of all Page URLs, do not request this report by calling that method directly: PiwikPluginsActionsAPI::getInstance()->getPageUrls($idSite, $period, $date);. Instead, issue a new API request:


$report = PiwikAPIRequest::processRequest('Actions.getPageUrls', array( 'idSite' => $idSite, 'period' => $period, 'date' => $date,
));

This has several advantages:

  • It avoids a fatal error if the requested plugin is not available on a Piwik installation
  • Other plugins can extend the called API method via events (adding additional report data to a report, doing additional permission checks) but those events will be only triggered when requesting the report as suggested
  • If the method parameters change, your request will most likely still work

Publishing your Plugin on the Marketplace

In case you want to share your API with other Piwik users you can do this by pushing your plugin to a public GitHub repository and creating a tag. Easy as that. Read more about how to distribute a plugin and best practices when publishing a plugin.

Isn’t it easy to create a API? We never even created a file! If you have any feedback regarding our APIs or our guides in the Developer Zone feel free to send it to us.

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