Fatal error: Cannot redeclare function (previously declared in php-wasm)

[Krinkle]

At https://3v4l.org/#live, when typing:

function x() {
}
x();

And then adding anything above or below it, the preview starts failing:

Fatal error: Cannot redeclare x() (previously declared in php-wasm run script:4) in php-wasm run script on line 5

Browser: Firefox 128 on macOS.