Using 3rd-Party Libraries

Yii is carefully designed so that third-party libraries can be easily integrated to further extend Yii's functionalities. When using third-party libraries in a project, developers often encounter issues about class naming and file inclusion. Because all Yii classes are prefixed with letter C, it is less likely class naming issue would occur; and because Yii relies on SPL autoload to perform class file inclusion, it can play nicely with other libraries if they use the same autoloading feature or PHP include path to include class files.

Below we use an example to illustrate how to use the Zend_Search_Lucene component from the Zend framework in a Yii application.

First, we extract the Zend framework release file to a directory under protected/vendors, assumingprotected is the application base directory. Verify that the fileprotected/vendors/Zend/Search/Lucene.php exists.

Second, at the beginning of a controller class file, insert the following lines:

Yii::import('application.vendors.*');
require_once('Zend/Search/Lucene.php');

The above code includes the class file Lucene.php. Because we are using a relative path, we need to change the PHP include path so that the file can be located correctly. This is done by calling Yii::import beforerequire_once.

Once the above set up is ready, we can use the Lucene class in a controller action, like the following:

$lucene=new Zend_Search_Lucene($pathOfIndex);
$hits=$lucene->find(strtolower($keyword));

Using namespaced 3rd-Party Libraries

In order to use namespaced library that follows PSR-0 (such as Zend Framework 2 or Symfony2) you need to register its root as path alias.

As an example we'll use Imagine. If we put the Imagine directory under protected/vendors we'll be able to use it like the following:

Yii::setPathOfAlias('Imagine',Yii::getPathOfAlias('application.vendors.Imagine'));
 
// Then standard code from Imagine guide:
// $imagine = new Imagine\Gd\Imagine();
// etc.

In the code above the name of the alias we've defined should match the first namespace part used in the library.

Using 3rd-Party Autoloaders

Some 3rd-Party libraries (for example PHPUnit) use their own class autoloaders, which perform class file inclusion by rules, which are different from the ones used in Yii autoloader. Since Yii uses PHP include path as a 'last source' of class files, registering such 3rd-party autoloaders may produce a PHP Warning:

include(PHPUnit_Framework_TestCase.php) [function.include]: failed to open stream: No such file or directory

In order to avoid such problem make sure any 3rd-party class autoloaders are registered before the Yii autoloader:

require_once('PHPUnit/Autoload.php'); // register 3rd-party autoloader
require_once('/path/to/framework/yii.php'); // register Yii autoloader
...

If 3rd-party class autoloader is coming as separated function or method, you may useYii::registerAutoloader() method to register it. In this case Yii will prepend it before own autoloader automatically.

require_once('/path/to/framework/yii.php'); // register Yii autoloader
...
Yii::registerAutoloader(array('SomeLibrary','autoload')); // register 3rd-party autoloader
...

You can also avoid problems with 3rd-party autoloader disabling usage of PHP include path by settingYiiBase::$enableIncludePath to false before starting application:

require_once('/path/to/framework/yii.php');
$configFile='/path/to/config/main.php';
Yii::$enableIncludePath = false; // disable PHP include path usage
Yii::createWebApplication($configFile)->run();

Using Yii in 3rd-Party Systems

Yii can also be used as a self-contained library to support developing and enhancing existing 3rd-party systems, such as WordPress, Joomla, etc. To do so, include the following code in the bootstrap code of the 3rd-party system:

require_once('path/to/yii.php');
Yii::createWebApplication('path/to/config.php');

The above code is very similar to the bootstrap code used by a typical Yii application except one thing: it does not call the run() method after creating the Web application instance.

Now we can use most features offered by Yii when developing 3rd-party enhancements. For example, we can useYii::app() to access the application instance; we can use the database features such as DAO and ActiveRecord; we can use the model and validation feature; and so on.