function a()
{
    $demi = '局部变量';
    b($demi);
}
function b($args)
{
    echo $args;
}
a();

All functions and classes in PHP have global scope and can be defined within a function and called outside, and vice versa.

Why can function b obtain the local variables of function a by passing parameters?

function tesxt()
{
    $var = 10;
    $echonumber = function($num) {
         echo $num;
    };
    $echonumber($var);
}
tesxt();

Similarly, why do anonymous functions also obtain variables of external functions by passing parameters?