money_format is not working with Vietnamese

money-format.php

$number = 1234.56;

// let's print the international format for the en_US locale
setlocale(LC_MONETARY, 'en_US');
echo money_format('%i', $number) . "\n";
// USD 1,234.56

// but if using vi_VN or vi_VN.UTF-8, not working
setlocale(LC_MONETARY, 'vi_VN');
echo money_format('%i', $number) . "\n";
// 1234.56

hope this can help:
https://www.php.net/manual/en/numberformatter.formatcurrency.php

$fmt = numfmt_create( 'vi_VN', \NumberFormatter::CURRENCY );
numfmt_format_currency($fmt, $product->price, 'VND')

result:
300.000 ₫