Mastering PHP 7

Understanding dependency injection

Throughout the introductory section, we touched upon passing dependency through the class __construct() method. There is more to it than just passing the dependent object. Let's consider the following three seemingly similar but different examples.

Though PHP has been supporting type hinting for quite a while now, it isn't uncommon to come across pieces of code, which are as follows:

<?phpclass App{    protected $config;    protected $logger;    public function __construct($config, $logger)    {        $this->config = $config;        $this->logger = $logger;    }    public function run()    {        $this->config->setValue('executed_at', time());        $this->logger->log('executed');    }}class Config{    protected $config = [];    public function setValue(