Middle DI

A modern PHP Dependency Injection Container that brings IDE autocompletion, type safety, and zero-configuration to dependency injection. Unlike traditional containers that use string-based service keys, Middle-DI generates strongly-typed methods during development, then caches optimized code for zero-overhead production performance.

Why Middle DI?

The issue with traditional containers:

$database = $container->get('database');        // What type? Runtime errors possible
$userService = $container->get('user.service'); // No IDE support, typos discovered late

The Middle-DI solution:

$database = $container->getDatabase();     // Returns PDO, full IDE support
$userService = $container->getUserService(); // Returns UserService, compile-time safe

Similar to Pimple's simplicity but with modern type safety and zero runtime overhead.

How It Works

Middle-DI uses compile-time code generation during development to transform your simple container definition into an optimized singleton container.

Simple Conventions:

• Services: get*() methods return singletons, accept optional string $name parameter only
• Factories: new*() methods create fresh instances, accept any parameters

Your Definition:

class Container
{
    // Services: singletons
    public function getDatabase(): PDO
    {
        return new PDO($this->config('db.dsn'));
    }

    public function getUserService(): UserService
    {
        return new UserService($this->getDatabase());
    }

    // Factories: fresh instances
    public function newUser(string $username, array $roles = []): User
    {
        return new User($username, $roles);
    }
}

Generated for Production (cached, opcache-optimized):

class Container__Compiled extends Container
{
    private array $__services = [];

    private function __service(string $method, ?string $instanceName = null)
    {
        $suffix = is_null($instanceName) ? '' : '.' . $instanceName;
        return $this->__services[$method . $suffix] ?? ($this->__services[$method . $suffix] = parent::{$method}($instanceName));
    }

    public function getDatabase(?string $instanceName = null): PDO
    {
        return $this->__service('getDatabase', $instanceName);
    }

    public function getUserService(?string $instanceName = null): UserService
    {
        return $this->__service('getUserService', $instanceName);
    }

    // newUser() remains unchanged - creates new instances
}

Basic Usage

<?php
use jschreuder\MiddleDi\DiCompiler;

class Container
{
    public function getDatabase(): PDO
    {
        return new PDO('mysql:host=localhost;dbname=app');
    }

    public function getUserRepository(): UserRepositoryInterface
    {
        return new UserRepository($this->getDatabase());
    }

    public function newUser(string $username): User
    {
        return new User($username);
    }
}

// Compile and use
$container = (new DiCompiler(Container::class))->compile()->newInstance();

// Services: same instances (singletons)
$db1 = $container->getDatabase();
$db2 = $container->getDatabase();
var_dump($db1 === $db2); // true

// Factories: different instances every time
$user1 = $container->newUser('alice');
$user2 = $container->newUser('bob');
var_dump($user1 === $user2); // false

Named Service Instances

Support multiple configurations of the same service type:

class Container
{
    public function getDatabase(?string $name = null): PDO
    {
        $dsn = match($name) {
            'readonly' => 'mysql:host=slave;dbname=app',
            'analytics' => 'mysql:host=analytics;dbname=app',
            default => 'mysql:host=master;dbname=app'
        };
        return new PDO($dsn);
    }
}

// Usage
$primary = $container->getDatabase();           // Default primary DB
$readonly = $container->getDatabase('readonly'); // Readonly replica
$analytics = $container->getDatabase('analytics'); // Analytics DB

Production Optimization

Cache compiled containers for maximum performance:

use jschreuder\MiddleDi\DiCachedCompiler;

$compiler = new DiCachedCompiler(
    new DiCompiler(Container::class),
    new SplFileObject('var/cache/container.php', 'c+')
);

$container = $compiler->compile()->newInstance($config);

In production, this runs as pure opcached PHP with zero container overhead. The generated code has no dependency on Middle-DI itself - it is just pure PHP.

Configuration Support

Use the included ConfigTrait for clean configuration handling:

use jschreuder\MiddleDi\ConfigTrait;

class Container
{
    use ConfigTrait;

    public function getDatabase(): PDO
    {
        return new PDO(
            $this->config('db.dsn'),
            $this->config('db.username'),
            $this->config('db.password')
        );
    }
}

$config = [
    'db.dsn' => 'mysql:host=localhost;dbname=app',
    'db.username' => 'user',
    'db.password' => 'pass'
];

$container = $compiler->compile()->newInstance($config);

Key Features

🚀 Zero Configuration

No YAML, XML, or array configuration. Just write PHP methods with clear return types. The get vs new prefix tells Middle-DI everything it needs to know.

💡 Full IDE Support

Complete autocompletion, type hints, and "Go to Definition" support. Refactoring tools work perfectly. No more guessing what $container->get('service_name') returns.

⚡ Zero Production Overhead

Development-time compilation generates cached PHP files. Production runs pure opcached code that compiles to native PHP speed with full opcache optimization.

🔒 Type Safety

All dependencies are strongly typed. Catch errors during development, not in production.

🎯 Pure Dependency Injection

Services remain completely decoupled from the container. No annotations, no string dependencies, no special interfaces—just regular PHP classes.

Extensibility Features

Add advanced functionality using the decorator pattern:

$compiler = new CircularDependencyCompiler(
    new DiCachedCompiler(
        new DiCompiler(Container::class),
        new SplFileObject('var/cache/container.php', 'c+')
    )
);

This is how the DiCachedCompiler was implemented, which is currently the only included decorator.

Requirements

• PHP 8.3 or higher

Perfect for projects wanting Pimple's simplicity with modern IDE support and optimal production performance.