Exam1 : 

class A {

	function b() {
		echo("Hello?");
	}

}

$Ac = new A;

$Ac->b();
///////////////////////////////////////////////////////////
Exam2 : 

class A {

	function a() {
		echo("Hello?");
	}

}

$Ac = new A;

$Ac->a();
///////////////////////////////////////////////////////////

Exam1 code is once run b function but Exam2 code is two run a function. It's bug?? or my miss?? >_<