What changes have been made to global variables in PHP >8.0 and how does it affect their usability within functions?

In PHP 8.0, global variables are no longer supported within functions by default. This means that you cannot directly access global variables within a function without explicitly declaring them as global using the `global` keyword inside the function. To fix this issue, you need to use the `global` keyword to declare the global variable within the function scope before using it.

$globalVariable = 10;

function myFunction() {
    global $globalVariable;
    echo $globalVariable;
}

myFunction(); // Output: 10