You might try opening your file as a web page and clicking on page in the tool bar; then select save as.  If this works you don't need unknown software.

To convert HTML to PHP just change the extension from .htm to .php. The difference between an HTML file and a typical PHP file is that the PHP file has additional code which can (only) be executed on a PHP server. The result of serving a PHP file is always HTML. So if you convert an HTML file to PHP you will get exactly the same output on the client side as with the HTML file.

 

I don't really understand what you want to achieve.