Dependency Injection in PHP using pimple

Question

I'm new to DI ,using Pimple. Using: php 5.3.5 (wamp), namespaces as well. I'm refactoring code, using it, but came to a problem (s):

I have my Container that extends from Pimple, lets call it PContainer.php:

class ReuseableContainer extends Pimple{

      private function initOutterClass(){
         $this['special_location_class'] = '\SpecialLocation';
         $this['special_location'] = function($c){return new $c['special_location_class']($c['location_details'],$c['location']);};
      }

      private function initGlobalFunctions(){
         $this['getGeneralDataFromArray'] = function($c){
             // returning a function
             return function($arr){
                 foreach ($arr as $key => $value){
                 // do something
                   $new_data = $c['general_data_type'];
                   $new_data->id = $value['id'];
                   $new_data->name = $value['name'];
                 }

         }          

      }

      public function __construct(){
          $this['location_class'] = '\Location';
          $this['location_details_class'] = '\LocationDetails';
          $this['general_data_type_class'] = '\GeneralDataType';
          // define some objects
          $this['location'] = function ($c) {
               return new $c['location_class']();
          };

          $this['location_details'] = function ($c) {
               return new $c['location_details_class']();
          };

          $this['general_data_type'] = function ($c) {
              return new $c['general_data_type_class']();
          };

          $this->initOutterClass();
          $this->initGlobalFunctions();
      }



}
global $container ;
$container = new Pimple();

// embed the SomeContainer container
$container['embed'] = $container->share(function () { return new ReuseableContainer(); });

Ok. So i got a SpecialHelper.php which holds:

final class SpecialLocation{
    public $name;
    public $location;
    public $picture;

    public function __construct($location){
        $this->location; // dependent on class: Location
    }
}

final class SpecialUser{
    private $id; 
    private $location;

    public function __construct(\Location $location,$id=''){
        $this->id = $id;
        $this->location = $location; // $container['embed']['location'];
}

and we got our GeneralHelper.php which holds:

final class Location{
    public $lat;
    public $lng;
    public function __construct($lat='',$lng=''){ $this->lat = $lat; $this->lng = $lng;}
}
final class LocationDetails{
    public $id;
    public $addresss;
    public function __construct($id='',$address=''){$this->id = $id; $this->address = $address;}
}
class GeneralDataType{
    public $id;
    public $name;
    public function getName(){ return $this->name;}
    public function getId(){ return $this->id;}
}

and we have our "Special Class" controller, which looks something like this:

final class SpecialController{

    public function foor($some_array){
        $this->doSomething($some_array);
    }

    private function doSomething($ret_value){
        // do something
        $arr = array();

        foreach($ret_value as $key => $value){
             $something = $container['embed']['getGeneralDataFromArray']($value);
             $special_location = $container['embed']['special_location'];
             $arr[] = special_location; 
        }
        return $arr;
     }
  }

Finally we have our main "driver", main.php

require('PContainer.php');
....
...
$some_array = array(....);
$special_controller = new SpecialController();
$special_controller->foor($some_array);

Problems: 1) I had to add initOutterClass function inside ReuseableContainer to decouple the "Special" classes, how could have i decoupled them in a better way? creating a new "special" 9container or something? as EVERYTHING now sitts inside the container.. same goes to the initGlobalFunctions()

2) regarding SpecialHelper.php: i have there SpecialLocation, which one of its properties is a \Location class, i've put it in the constructor , but if i have 20 object properties that are dependent, i must put them all as INPUT params for the constructor?? same goes to the SpecialUser class, it has a $location which if i could i would have made $this->location = $container['embed']['location']; instead of $this->location = $location; resulting in a dependent on the DI! :/

3) I've had to create SpecialHelper.php in a different file, despite wanting to put it in the "special class controller", just so there won't be any unknowns (due to require statement order)

4) MOST importantly: about the "Special class" controller, how do i solve the doSomething method? i must create "Special Location" object inside the loop but i get that $container is unrecognized (despite being global, as of scope probably) but more over it's really dependent! and it's a private function, i don't wish to pass the container to EVERY class i'll use from now on, it isn't IoC right?

Any help is appriciated... i'm trying to understand the best practices..

Thank you

Answer 1

4)Most important: IoC is correct. That an implementation is not correctly working does not reflect the principle of IoC itself.

If you want to use the global $container within a function, then should you use the global keyword within that function. That is how PHP works. Making it static is solving the problem of reference, but does not make a real difference.

An IoC container resolves the dependencies for the caller. The caller does not have to know anything about the internals of the callee - and he doesn't care either. So, there should be some kind of contract by which the exchange of data is regulated. If you have that situation, then you have IoC.

3)That problem is too vague to answer, but imo also not relevant from a practical perspective. Does it work? Ok, good to know. :-)

2)The clue of IoC is the use of contracts. The IoC container is there to connect the caller to the proper contract. The contract resolves to a concrete callee. The callee will return information inline with the contract. The caller understands the answer. Therefor will you need that the input and output in this process is independent of a certain implementation at a certain time. So don't use 20 object properties as input, but use an array or general object instead.

1) I get the idea that you are mixing functional flow (data flow) with technical flow (relationships between classes). An IoC container serves the purpose of the technical flow, it optimizes the dependency in the relationships between classes. For instance, if you want to connect to a database, then might you reuse an existing connection instead of creating new connections all the time. Or if you want to use a special functionality on several moments in your flow, then might you use IoC for that.