Sold iPhone 4 but now worried about whether the data can be accessed?

My boyfriend just sold his old iphone 4 to a friend, and instead of wiping it out by going to settings -> General -> Reset -> Erase all content and settings, he just manually deleted all the pictures, apps, web history etc. He also left the password lock on and told his friend what the code was. Is there a possibility of his friend being able to recover what was on his phone? Or was his manually erasing everything good enough to ensure that his data and stuff won't be accessible

It wouldve been better if he restored it. I think its still possible if he knows a lot Of tech stuff

Yeah even if you did the erase all and restore it to factory after that its still possible to get data… ( my friend did that same thing) and i restored the data for him