What is a Dependency Injection

Dependency Injection is where components are given their dependencies through their constructors, methods, or directly into fields.

Constructor Injection

class User
{
    function __construct($storage)
    {
        $this->storage = $storage;
    }
    
    // ...
}

Setter Injection

class User
{
    function setSessionStorage($storage)
    {
        $this->storage = $storage;
    }
    // ...
}

Property Injection

class User
{
    public $sessionStorage;
}
    
$user->sessionStorage = $storage;

As a rule of thumb, constructor injection is best for required dependencies, like in our example, and setter injection is best for optional dependencies, like a cache object for instance.

Installation

• git clone https://github.com/bakhtiyor/dependency-injection
• cd dependency-injection
• composer install
• php example/di-test.php

Credit

http://fabien.potencier.org/what-is-dependency-injection.html