Les Functions

if (!\function_exists(u::class)) {
    function u(?string $string = ''): UnicodeString
    {
        return new UnicodeString($string ?? '');
    }
}

use function Symfony\Component\String\u;

pour utiliser la function

namespace Symfony\Component\String;
 
if (!\function_exists(u::class)) {
    function u(?string $string = ''): UnicodeString
    {
        return new UnicodeString($string ?? '');
    }
}