keep photos on iphone but not on icloud
I do not send my photos to iCloud, i only keep them on my phone. 

All you need to do is toggle of the switch that tells your phone to send your photos to iCloud or not. 

When you are in the iCloud settings page you can choose what things you want to have iCloud save, such as calendar, notes etc by just toggling a switch/button next to each function.  

Go to Settings and click on your name at the top of the page, it will  be at the top of the page and have your name in large text ( or whatever your apple id is set to ) and in small text just below it will be "Apple ID,iCloud, iTunes &amp; APP Store with a  >  to the right. 

Touch the > scroll down and touch iCloud, now just toggle off the slider button next to Photos. ( it will be green and to the right if it is set to on and if you touch it it will move the the left and no longer be green. )  

I also do not use iCloud drive, i keep it toggled off. ( not sure if having it on would have an effect on the photos setting.