PHP-NTL is a PHP library that convert Int number to String letters from 0 to 999,999,999,999. Also, Two langages available by default French and other English. This library is very usefull for web application especially for Facturation.
You need to require the file NumberToLetter.php and create new instance of NumberToLetter class, with Two params($number, $lang), if you use only one params the second params will be 'FR'. And then use the method ->NumberToLetter().
You can make many test by using the method ->maketest($from, $to, $lang)
Just fork this repository and make a Pull Request