包含文件中声明的方法的PHP范围[重复]

Can someone explain how files are included inside methods. Here is what I don't understand: Let's say we have 2 files:

//a_variable.php
$variable=1;

And

//b_variable.php
$variable++;

Upon calling call_variable() from:

class TestView
{
    public static function a_variable()
    {
        require 'View/test/a_variable.php';
    }

    public static function b_variable()
    {
        require 'View/test/b_variable.php';
    }

    public static function call_variable()
    {
        self::a_variable();
        self::b_variable(); //doesn't know $variable. As expected.
    }
}

I get "Undefined variable: variable", which is expected, because $variable has only local scope inside the a_variable() method.

But, exactly the same code, using methods:

//a_method.php
function method()
{
    echo "a";
}

And

//b_method.php
function method()
{
    echo "b";
}

Upon calling call_method() from:

class TestView
{
    public static function a_method()
    {
        require 'View/test/a_method.php';
    }

    public static function b_method()
    {
        require 'View/test/b_method.php';
    }

    public static function call_method()
    {
        self::a_method();
        self::b_method(); //DOES know method(). Why?
    }
}

I get "Fatal error: Cannot redeclare method() (previously declared in View\test\a_method.php:4) in View\test\b_method.php on line 5"

Why is the name of the included method visible outside the scope of the caller method?

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