Develop a PHP-based sitemap-XML generator

I need someone to Develop a PHP-based sitemap-XML generator , which will take as input a big .txt file which is a simple list of URLs (it must take this file from the server and not from browser upload). Also, it must make each sitemap to have 50,000 entries max, meaning if there are more than 50,000 entries, then it splits the resulting files into multiple files, like [login to view URL], [login to view URL], [login to view URL], etc.