Define/include "globally available" arrays and functions

You can use the new Files autoloading available to the Autoloader as of v4.1.2. Create a class containing your global functions and defining your currencies as constant.

PHP Code:

// example filename: my_global_functions.php

define('CURRENCIES', array('EUR', 'USD'));

if (! function_exists('foo'))
{
    function foo()
    {
            // logic here
    }
} 


After creating the file, write the path of the file in your app/Config/Autoload.php file, particularly in the $files property.

PHP Code:

// app/Config/Autoload.php

public $files = [
    'path/to/my_global_functions.php',
];