Playing solely against chess engine? I don't have many friends to play chess with that are at my skill level so many times I am forced to play against the computer. It seems like the computer plays much differently than a human, or at least, so I hear. 

Is it necessary to play against humans to increase your ability or can playing against the computer yield the same result?
Playing against an engine is definitely still good practice for your chess. You can typically scale the strength of the engine to make it harder or easier depending on your level. In my experience it tends to be bit boring since most engines tend to favour particular openings and a fairly aggressive style of play.  To combat this you can tell the engine to play a certain line, but this also takes some of the excitement out since you know in advance what the engine will play.

Aside from engines there are always plenty of online options to find a game. For example chess.com is a free site where you can play against basically any strength player. It also offers live matches as well as correspondence games. You can filter by ELO rating to find games against opponents who would suit your skills.