Site Help: Spider Identification Request, 1 by Essay

Essay wrote:
I've got an orb spider in my arbor vitae that I've never seen before. The picture doesn't do it justice; the yellow is actually an iridescent green/gold color when the the little guy is in direct sunlight. The spider is less than an inch long, legs included, and returns to the same spot each day to spin a new web. I regularly get American garden orb spiders late in the summer, but they are much larger and have plump bodies rather than the flattened abdomen this spider has. Is this a juvenile or male, or is this a different kind of spider entirely? I live in Pennsylvania, twenty miles northwest of Philadelphia.