PHP静态方法init $ _SESSION var？

Question

I found strange feature with $_SESSION var

class A
{
    static function doSomething()
    {
        $_SESSION['foo'] = 'bar';
    }
}

A::doSomething();

var_dump($_SESSION);

As you may guess session is not started but $_SESSION var is initialized. Who can explain what actually happens?

Answer 1

The $_SESSION is a superglobal array:

By default, all of the superglobals are available...

So you can always access this array. This would also work when there was no POST Request, but you could do $_POST['foo'] = 'bar'.

When you try to go to another page in your example, where you don't call A::doSomething, you will see, that echo $_SESSION['foo']; will throw an error, since you didn't call session_start();.