How do I fetch the PHP DI container? - php

Question

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

Answer 1

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.