PHP Methods Static

Question

PHP allows me to have methods static. Whose advantage is to have them accessible without the need to instantiate the class Documentation.

However, in the case of methods static, I can use them both ways WITHIN THE CLASS ITSELF:

class Teste
{
    private static metodoEstatico()
    {
        //código
    }

    public outroMetodo()
    {
        self::metodoEstatico(); 
        $this->metodoEstatico();
    }
}

PHP allows you to use static methods, both ways, within the class itself. Is there any difference in performance or something relevant to the two forms of use being within the class itself?