Magento: ignore everything except just one file

I’ve been having the entry /public_html/feeds in my Magento project’s root directory so that none of the contents in feeds directory is tracked. But I need to track one file here which is .PHP file. How do I go about changing this entry so that only the .PHP files are tracked by the git?

What I did is !/public_html/feeds/*.php but this tracks everything now instead of one ending in .php