Third party iPhone charger? How fast can it cause damage?

I have always known using third party no name iPhone chargers can wreck your iPhone and stop it from charging properly, so I avoided. But I plugged my iPhone into my friends charger which I realized after was not an apple charger, it was only plugged in for 5-10 minutes before I removed it- could it possibly have already done some damage to my phone? I can't tell if my phone is charging slower or if I'm worrying myself over nothing!

It is unlikely that the charger did any damage. Anything that can provide clean USB power will work, although I still prefer Apple chargers myself.

As long as it is a 5V power source, the make of it has no effect, it will charge the phone exactly the same.

I routinely use a cheap four-output charger for my iphone and other gadgets as it's more convenient that several individual chargers.

It will not do any harm.