phpoopdependency-injectioncontainersphp-di

How do I fetch the PHP DI container?


How do I load a database container using PHP DI? This is one of the variations I have tried up until now.

Settings.php

<?php 
use MyApp\Core\Database;
use MyApp\Models\SystemUser;

return [
    'Database'      => new Database(), 
    'SystemUser'    => new SystemUser()
];

init.php

$containerBuilder   = new \DI\ContainerBuilder(); 
$containerBuilder->addDefinitions('Settings.php');
$container          = $containerBuilder->build();

SystemUserDetails.php

<?php 
namespace MyApp\Models\SystemUser;

use MyApp\Core\Database;
use MyApp\Core\Config;
use MyApp\Helpers\Session;


/**
 *
 *  System User Details Class
 *
 */
class SystemUserDetails 
{

/*=================================
=            Variables            =
=================================*/

    private $db;


/*===============================
=            Methods            =
================================*/

    /**
     *
     *  Construct
     *
     */
    public function __construct(Database $db)
    {
        # Get database instance
        // $this->db           = Database::getInstance();
        $this->db           = $db;
    }


    /**

Too few arguments to function MyApp\Models\SystemUser\SystemUserDetails::__construct(), 0 passed in /www/myapp/models/SystemUser.php on line 54 and exactly 1 expected File: /www/myapp/models/SystemUser/SystemUserDetails.php

Shouldn't the database get loaded automatically?

Trace:

  1. Currrently, My main index.php file extends init.php which is the file where it create the container (pasted code part in the post).

  2. Then I call the App class, which fetches the URL(mysite.com/login/user_login) and instantiate a new controller class and run the mentioned method, in this case, it's the first page - MyApp/Contollers/Login.php.

    1. The user_login method fetches the credentials, validate them, and if they are valid, uses the SystemUser object to login.

SystemUser class:

namespace MyApp\Models;


class SystemUser
{

    public $id;

    # @obj SystemUser profile information (fullname, email, last_login, profile picture, etc')
    protected $systemUserDetatils;


    public function __construct($systemUserId = NULL)
    {
        # Create systemUserDedatils obj
        $this->systemUserDetatils   = new \MyApp\Models\SystemUser\SystemUserDetails();

        # If system_user passed
        if ( $systemUserId ) {

            # Set system user ID
            $this->id                   = $systemUserId;

            # Get SysUser data
            $this->systemUserDetatils->get($this);

        } else {

            # Check for sysUser id in the session:
            $systemUserId                   = $this->systemUserDetatils->getUserFromSession();

            # Get user data from session 
            if ( $systemUserId ) {

                # Set system user ID
                $this->id                   = $systemUserId;

                # Get SysUser data
                $this->systemUserDetatils->get($this);
            }
        }
    }
}

Solution

  • PHP-DI is working correctly.

    In your SystemUser class you are doing:

    $this->systemUserDetatils   = new \MyApp\Models\SystemUser\SystemUserDetails();
    

    The constructor for SystemUserDetails requires a Database object, which you are not passing.

    By calling new directly, you are not using PHP-DI. By doing this you are hiding the dependency, which is exactly what you are supposedly trying to avoid if you want to use a dependency injection system.

    If SystemUser depends ("needs") SystemUserDetails, the dependency should be explicit (e.g. declared in its constructor).

    Furthermore: You do not need a definitions file for a system like this. And the definitions file you show in your question doesn't follow the best practices recommended by PHP-DI.

    Your design is far from perfect, and I'm not sure of your end-goals, but if you did something like this, it could work:

    <?php
    // src/Database.php
    
    class Database {
        public function getDb() : string {
            return 'veryDb';
        }
    }
    
    <?php
    // src/SystemUserDetails.php
    
    class SystemUserDetails {
    
        protected $db;
    
        public function __construct(Database $db)
        {
            $this->db           = $db;
        }
    
        public function getDetails() {
           return "Got details using " . $this->db->getDb() . '.';
        }
    }
    
    <?php
    // src/SystemUser.php
    class SystemUser {
    
        protected $details;
    
        public function __construct(SystemUserDetails $details, $userId=null) {
    
            $this->details = $details;
        }
    
        public function getUser() {
           return "Found User. " .$this->details->getDetails();
        }
    }
    
    <?php
    //init.php
    require_once('vendor/autoload.php');
    
    // build the container. notice I do not use a definition file.
    $containerBuilder   = new \DI\ContainerBuilder();
    $container          = $containerBuilder->build();
    
    // get SystemUser instance from the container.
    $userInstance = $container->get('SystemUser');
    
    echo $userInstance->getUser(), "\n";
    
    

    Which results in:

    Found User. Got details using veryDb.