What is the difference between new self() and new static() in PHP

This article mainly shares with you the difference between new self() and new static() in PHP. I hope it can help you.

1.new static() is a new feature introduced in PHP5.3 version.

2. Whether it is new static() or new self(), a new object is new.

3. What is the difference between the objects produced by new from these two methods? To put it bluntly, is the object produced by new the same class instance or a different class instance?

In order to explore the above problem, we first put a simple code:

class Father {    public function getNewFather() {        return new self();
    }    public function getNewCaller() {        return new static();
    }

}$f = new Father();print get_class($f->getNewFather());print get_class($f->getNewCaller());注意，上面的代码get_class()方法是用于获取实例所属的类名。

The result here is: whether calling getNewFather() or getNewCaller(), the result returned is the Father class Example.

The printed result is: FatherFather

At this point, it seems that there is no difference between new self() and new static(). Let's go on:

 Sun1  Sun2  (-> (-> (-> (->getNewCaller());看上面的代码，现在这个Father类有两个子类，由于Father类的getNewFather()和getNewCaller()是public的，所以子类继承了这两个方法。

The printed result is: FatherSun1FatherSun2

We found that whether it is Sun1 or Sun2, the object returned by calling getNewFather() is an instance of the Father class, and getNewCaller () returns the caller's instance.

That is, $sun1 returns an instance of the Sun1 class, and $sun2 returns an instance of the Sun2 class.

Now I seem to understand the difference between new self() and new static().

First of all, their difference can only be reflected in inheritance. If there is no inheritance, then there is no difference between the two.

Then, the instance returned by new self() is unchanged for thousands of years. No matter who calls it, it will return an instance of the same class, while new static() is determined by the caller.

$sun1->The caller of getNewCaller() above is $sun1, right! $sun1 is an instance of class Sun1, so what is returned is an instance of class Sun1. The same reason for $sun2 will not be repeated.

Okay, that’s all for now about the difference between new self() and new static() in PHP. I hope it will be helpful to readers’ understanding. If there is something wrong, please feel free to throw it out there.

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