It is nice to have a friend to talk,laugh and do things with

It is nice to have a friend to talk,laugh and do things certainly.
这句子是形式主语,真正主语是不定式：to have a friend to talk,laugh and do things certainly.
to have a friend to talk,laugh and do things certainly is nice.是正常语序,用It这样表达是为了防止头重脚轻.所以主语用不定式来表达,it做形式主语.