>> There is a second form of Dependency Injection that uses setters instead of constructor injection. Do not use this form. >Why? Not using setter injection el

>> There is a second form of Dependency Injection that uses setters instead of constructor injection. Do not use this form. >Why? Not using setter injection eliminates a huge class of bugs that occur when people try to use objects that haven't had all of their dependencies injected yet: $user = new RegisteredUser(); // Any code that touches $user here will be bad $user->setEmail($email); > constructor injection can become a nightmare. Which is why people use library to do it for them - an example for PHP https://github.com/rdlowrey/auryn https://github.com/rdlowrey/auryn.