Why is a method with the same name as the class being called automatically?

Question

EDIT: Title edited to make it more useful. Originally I had no idea that it was the use of a shared word that was causing the problem.

This is very basic but rather mysterious.

I have two classes:

class Hello
{
        public function hello()
    {
        echo "Hello";
    }
}

and

class World
{
    public function world()
    {
        echo " World";
    }
}    

called by

include_once 'classes/Hello.php';
include_once 'classes/world.php';

$hi= new Hello;    
$wd= new World;`

Result Hello World

I originally accidentally had hello for the name of the class World's method. Result Hello i.e. no World.

Question 1

Why are the methods firing? I have instantiated two objects but have not requested that the method “fire”. I thought I would have to do something like:

$hi->hello();

to get an output.

Question 2

I am even more mystified that I only get Hello if both functions are called hello.

Surely

$hi= new Hello;
$wd= new World;

instantiates two completely separate objects. So how does the actual NAME of a method affect anything?

I have a long way to go but this really confused me.

Answer 1

Both methods get called, when you create a new instance of this class, because the methods have the same name as the class itself and so they are the constructor of this class:

class Hello
{
        public function hello()
    {
        echo "Hello";
    }
}

class World
{
    public function world()
    {
        echo " World";
    }
}

So when you took an instance from both classes, both constructors got called.

Now when you renamed both methods to hello only 1 method was counted as constructor and the other one was a normal method in the other class. That's why you only saw Hello as output.

---

But don't use the name of the class as constructor! It will be deprecated in PHP 7. Use __construct().