A simple array of strings will do if you have any programming skills. Create a for each loop (or for loop throughout the whole array) and recreate the string by dividing the string with '.' as delimiter, so that home.php becomes home and php, replacing second item and then creating string from substrings again. If you only intend to rename php files to html files, you can simply replace every occurence of php with html.
This can be achieved with every scripting and programming language possible, so let us know if you need simple example in language which syntax you're familiar with.