Call to undefined function with PHP

I have this class:

class testclass{
    function func1(){
        return "hello";
    }
    function func2(){
        echo func1();
    }
}

When I am running

$test = new testclass();
$test->func2();

I get an error: Fatal error: Call to undefined function func1() with the line index of echo func1();

My question now is, how do I make the func2 recognize func1

Is this a problem with the scopes?

Solution

function func2(){
        echo func1();
    }

should be

function func2(){
        echo $this->func1();
    }