Php script running but not working

I’ve installed php using this guide. It worked and my script seems to work with

php /var/www/html/folder/file.php 

At least it doesn’t give me an error message. The script sends a get request to an outside API which is then written to a .txt file. I then read it on page load with javascript and display it on my site. The problem is that none of the text files get updated. It works on my local apache server that I set up on my computer, but not on my website. I know it’s probably better to use mySQL but that’s not something I know how to do (though I am planning to learn).