External Variables of Functions in PHP

Variables declared outside of a function are not visible inside. Let's look at an example. Suppose we have the following variable:

<?php
	$num = 1;
?>

Let's try to output this variable inside a function:

<?php
	$num = 1;
	
	function func()
	{
		echo $num;
	}
	
	func(); // error
?>

Explain what the result of the code execution will be:

<?php
	$aaa = 111;
	
	function func()
	{
		echo $aaa;
	}
	
	func();
?>

Explain what the result of the code execution will be:

<?php
	$num1 = 1;
	$num2 = 2;
	
	function func()
	{
		return $num1 + $num2;
	}
	
	echo func();
?>