Pros of PHP-Centric Side projects

I have built a few database systems with PHP and MySQL, with the system relying heavily on PHP. I use minimal Javascript on my side projects due to the fact that I have no control over web browser updates, nor do I have control over the intended users of my products habit of updating their browsers, which is a prerequisit of running PHP-MySQL system. I am aware that intigrating Javascript functions in web pages imrpoves functionality signifaicantly, but that the whole system would potentially brake and will be rendered unsuable for some time. Due to my clients are mostly small businesses and has no in-house I.T programmer, and assuming that they might not find other willing or able developers in my area if I'm not able to address their problems with browser compatibility.