>>PE = mgh (I know this, because those are my initials)
>>
>>So when we solve for a photon, which has a mass (m) of zero, the result is no gain in potential energy.
>
>A photon does not have a mass zero. Since it has energy, it must also have mass. If physisists say that it has a rest mass of zero, this simply means that a photon moves at the speed of light. The "rest mass" of any particle moving at the speed of light can't be different from zero, or else, at the speed of light, it would have an infinite mass.

Rest mass = mass:

Sometimes people will use the phrase "rest mass," or "invariant mass," but this is just for emphasis: mass is mass.
http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html

The most common perspective in physics is that the photon is massless. The above webpage explores the question a little more, but you'll that its conclusion is that if the photon does have mass, alot of physics is toast.


>Like a "regular" particle, a photon has mass, energy, and momentum (mass x velocity), gravitational attraction, among others.

Does light have mass?

The short answer is "no", but it is a qualified "no" because there are odd ways of interpreting the question which could justify the answer "yes".

Light is composed of photons so we could ask if the photon has mass. The answer is then definitely "no": The photon is a massless particle.
http://math.ucr.edu/home/baez/physics/Relativity/SR/light_mass.html

Most physicists would disagree with you that a photon has mass; and most would disagree that any object feels "gravitational attraction" because in general relativity gravity is not an attractive force, it is the geometry of space-time.