Briefly talk about php delayed static binding

Usage scenario

First observe the following code:

abstract class base {
  //do sth
}
class aClass extends base{
  public static function create(){
    return new aClass();
  } 
}
class bClass extends base{
  public static function create(){
    return new bClass();
  }
}
var_dump(aClass::create());
var_dump(bClass::create());

Output:

object(aClass)#1 (0) { } object(bClass)#1 (0) { }

The above aClass and bClass inherit from the abstract class base, but the static method create() is implemented in both subclasses at the same time. Following the oop idea, this repetitive code should be implemented in the parent class base.

Improved code

abstract class base {
  public static function create(){
    return new self();
  } 
}
class aClass extends base{
}
class bClass extends base{
}
var_dump(aClass::create());
var_dump(bClass::create());

The current code seems to be in line with our previous ideas. The create() method is shared in the parent class. Let's run it and see what happens.

Cannot instantiate abstract class base in...

Unfortunately, the code does not seem to run as we expected. self() in the parent class is parsed to the parent class base, and does not inherit from his children. kind. So in order to solve this problem, the concept of delayed static binding was introduced in php5.3.

Delayed static binding

abstract class base {
  public static function create(){
    return new static();
  } 
}
class aClass extends base{
}
class bClass extends base{
}
var_dump(aClass::create());
var_dump(bClass::create());

This code is almost the same as the previous one. The difference is that self is replaced with the static keyword. static will be resolved to a subclass instead of a parent class, so that the above problem can be solved. The problem I encountered is PHP's delayed static binding.

Finally, run the code and get the final desired result.

object(aClass)#1 (0) { } object(bClass)#1 (0) { }

The above has introduced a brief talk about PHP delayed static binding, including aspects of the content. I hope it will be helpful to friends who are interested in PHP tutorials.