What is dependency injection?

Dependency inversion (DIP): Dip is a design idea, in the traditional software design, the upper layer of code relies on the lower layer, when the underlying code changes, the upper code will be changed, the code is difficult to maintain, and the DIP design concept requires the definition of the upper interface, the lower layer to implement this interface, thereby reducing the coupling degree.

Inversion of Control (IOC): The IOC is a specific approach to dip, which will be implemented by third parties by the lower layer on which it relies. That is, to proactively get the required external resource C in Class A, which is referred to as positive. So what's the reverse? is a class no longer master to acquire C, but passively wait, waiting for the Ioc/di container to get an instance of C, and then injected into the reverse of the Class A.

Dependency Injection (DI):D i is a design pattern for the IOC that moves the instantiation of a class from another class to an external implementation of the class.

Dependency injection is the implementation:

1. Define an interface or abstract class (this is an example of sending an email)

Interface mail{public    function Send ();}

2. Different types of send implement this interface

Class Email implements Mail () {public    function send ()    {        //Send email    }}

Class  Smsmail implements Mail () {public    function send ()    {        //Send SMS    }}

3.

   __construct (->_mailobj =          ->_mailobj->send ();

$reg = new Register ();
$EMAILOBJ = new Email ();
$SMSOBJ = new Smsmail ();

$reg->doregister ($EMAILOBJ);//Use email to send
$reg->doregister ($SMSOBJ);//Send Using SMS