PHP’s new static and new self

Let’s give a chestnut below:

class Father {
    public static function getSelf() {
        return new self();
    }
    public static function getStatic() {
        return new static();
    }
}
class Son extends Father {}
echo get_class(Son::getSelf()); // Father
echo get_class(Son::getStatic()); // Son
echo get_class(Father::getSelf()); // Father
echo get_class(Father::getStatic()); // Father

new self

Note here that this line get_class(Son::getStatic()); returns Son. class, can be summarized as follows:

self returns the class in which the keyword new in new self is located, such as the example here:

public static function getSelf() {
    return new self(); // new 关键字在 Father 这里
}

always returns Father.

new static

static Based on the above, it is a little smarter: static will return the class that executes new static(), such as Son executing get_class(Son: :getStatic()) returns Son, Father. Executing get_class(Father::getStatic()) returns Father

. In the absence of inheritance, it can be considered that new self and new static return the same result.

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