What is the proper way to convert ip to integer in php?

So I need to store IP addresses in database, but storing them as stings is not very efficient and not very convenient for my purpose.

So... How can I convert ip into integer in php with as less processing as possible because it will be done millions of times a day.

And of course how can I convert back from integet to ip?

I know this can be googled and there's some easy solutions - but I'm asking for the fastest way, not just for "do X and you get Y" because it's actually pretty easy task.