Phals don't mind light but it can not be direct, that will burn the leaves. Bright light with a barrier(white curtain) in between the (sun)window and phal works well. Most people overwater their Phals as they can go very dry before watering. It is imperative to examine your medium. Is your Phal planted in potting soil? (not good), with a lot of moss? (that can keep the roots too wet creating rot), was water allowed to sit in the crown (more rot) ?
Phals get their nutrients from the air and water. Were the roots allowed to breathe?(goes back to medium) Did you mist the roots when they did appear dry? Did you give your phal a good soaking when you did water it. Did you let it drain through? Did you allow water to sit and collect at the base of the container your phal was place in or on? (bad idea)
How did your phal look as it was depleting in health? What noticeable changes occurred to the plant?
Please feel free to share your information so you can be directed as what to do for your new phal and prevent it from succumbing to the same circumstances your last phal did!
Phals aren't difficult to maintain and keep .. you just have to know what to do to make them happy!