[PHP] Dependency Injection Implementation

[jean-baptiste verrey]

Hi everyone,

Dependency Injection is a very trendy subject and after reading about it I
kinda thought about rewriting the framework I'm doing with dependency
injection. So I made my own implementation and was wondering what would you
think about it? I have followed the article of Martin Fowler (
http://martinfowler.com/articles/injection.html)

with this implementation I have the following :
- you have both constructor and setter injection
- the Dependency class is a service locator
- we have at the same time service locator AND dependency injection
- you can always manually inject dependency
- you can pass arguments to the injected object constructor

So: am I missing something? Do you think it's good enough?

here is the code :
<?php
class Dependency {
    protected $_singletonInstances = array();
    protected $_setInstances = array();
    protected $_configuration;

    public static function getInstance() {
        static $instance = NULL;
        if (NULL === $instance) {
            $instance = new static();
        }
        return $instance;
    }

    public function setConfiguration(array $configuration) {
        $this->_configuration = $configuration;
    }

    public function getConfiguration() {
        return $this->_configuration;
    }

    public function __isset($serviceName) {
        return isset($this->_serviceInstances[$serviceName]);
    }

    public function __call($serviceName, $args) {
        // singleton
        if (isset($this->_configuration[$serviceName]) &&
$this->_configuration[$serviceName]['singleton']) {
            if (!isset($this->_singletonInstances[$serviceName])) {
                $rc = new
\ReflectionClass($this->_configuration[$serviceName]['class']);
                $this->_singletonInstances[$serviceName] = empty($args) ?
$rc->newInstance() : $rc->newInstanceArgs($args);
            }
            $ret = $this->_singletonInstances[$serviceName];
        } else {
            // normal
            if (isset($this->_setInstances[$serviceName])) {
                $ret = $this->_setInstances[$serviceName];
                unset($this->_setInstances[$serviceName]);
            } else {
                $rc = new
\ReflectionClass($this->_configuration[$serviceName]['class']);
                $ret = $this->_singletonInstances[$serviceName] =
empty($args) ? $rc->newInstance() : $rc->newInstanceArgs($args);
            }
        }
        return $ret;
    }

    public function __get($serviceName) {
        return $this->__call($serviceName, array());
    }

    public function __set($serviceName, $instance) {
        if (!is_object($instance))
            throw new Exception('instance must be an object');
        $this->_setInstances[$serviceName] = $instance;
    }
}
class DependencyInjectorException extends \Exception {

}

$di=DependencyInjector::getInstance();
$di->setConfiguration(array(
    'database.connector'=>array(
        'singleton'=>true,
        'class'=>'DatabaseConnector'
    ),
    'database'=>array(
        'singleton'=>true,
        'class'=>'Database'
    )
));

class DatabaseConnector{}
class Database{
    protected $_connector;
    public function __construct(){

$this->setConnector(DependencyInjector::getInstance()->{'database.connector'});
    }

    public function setConnector($connector){
        $this->_connector=$connector;
    }
}
class Test{
    protected $_database;
    public function __construct(){
        $this->setDatabase(DependencyInjector::getInstance()->database);
    }

    public function setDatabase($db){
        $this->_database=$db;
    }

    public function getDatabase(){
        return $this->_database;
    }
}

$test=new Test();
var_dump($test->getDatabase());

?>