PHP：实例化一个类并使用另一个类的方法

Question

I have a class, named A. I have another class named B that extends A. I must instantiate A, and not B, but I need to use the methods in B too. How can I do this?

Class A
{
    public function foo() { }
}

Class B extends A
{
    public function bar() { }
}

$a = new A();
$a->bar();

I know that this is not possible, but I need of a solution for this.

PS: I wish the title of this question is correct.

Answer 1

$a = new A();
$a->bar();

Will give you fatal error. Because bar() is not a method of class A . So you can't call this using A class's object.

This will work fine:

Class A
{
   public function foo() { }
}

Class B extends A
{
   public static function bar() {  }
}

$a = new A();
B::bar();

Answer 2

I think, you just misunderstood the syntax of PHP ( Which can be rather confusing sometimes )

The extends keyword does not extend the parent class ( A ), but does create a new class B which is a child of A . B inherits A 's methods, but A itself is not altered.

Answer 3

Can the methods in B become static?

Class A
{
    public function foo() { }
}

Class B extends A
{
    public static function bar2() { }
}

$a = new A();
$a->bar();
B::bar2();

obviously it would make sense to name it something different, as B::bar() is overriding the A::bar() implementation.

I think you might have your structure slightly off. Try to abstract what you want as a reusable code snippet into its own routine.