Call function of class ONE from class TWO without

问题:

If i have two classes A, B and one does not extend another they are separate but both loaded into script can i still reference function in A from B?

class A {
    function one() {
        echo "Class A";
    }
}

class B {
    function two() {
        echo "Class B";
        A::one();
    }
}


$a new A; 
$b = new B;

$b->two();

回答1:

On the face of it, yes, you can do this. However, function one() in class A needs to be declared as static for your call notation to work. (This makes it a class method.)

The other alternative, suggested by the last lines in your code, is for the instance $b to call a function in instance $a. Such functions are called instance methods and are how you normally interact with an object. To access these methods, they must be declared as public. Methods declared as private can only be called by other methods inside that class.

There are several ways to call an instance method in your code. These are the obvious two you can pass in $a as a parameter to the function, or you can create an instance of class A inside your method.

What are you actually trying to achieve?

回答2:

You can define it like this.

class A {
    public static function one() {
        echo "Class A";
    }
}

class B {
    function two() {
        echo "Class B";
        A::one();
    }
}


$a new A; 
$b = new B;

$b->two();

回答3:

You can define one as static, but why would you do such a thing?