How to configure reverse DNS?

I got a static IP from my ISP and a domain from GoDaddy. I configured DNS in GoDaddy to point to my static IP. So the website works. However, when I tried to lookup reputation of the IP address, I figured out that the reverse DNS points to my ISP’s domain and hostname. I’ve contacted the ISP for configuring reverse DNS on their end, but they said that they don’t provide such a service (though I’m not sure whether the person I talked to has the correct info).

create ini file, write values in PHP

I cannot find a way that easily lets me create a new file, treat it as an ini file (not php.ini or simiilar… a separate ini file for per user), and create/delete values using PHP. PHP seems to offer no easy way to create an ini file and read/write/delete values. So far, it’s all just “read” – nothing about creating entries or manipulating keys/values.