This zoo is a conservation zoo and actually cares about their animals. That alone gives it 5 stars in my book. I saw a lot of people compare this zoo to World Wildlife and it makes me sad. That zoo is for profit and their animals suffer as a result. It's all about the money for them.
I love this zoo. They have tons of programs and classes for families and adults. They really get the community involved. Their mission is conservation and they are not for profit, so their focus on the animals and their welfare.
My family has a membership here and we go about once per month. It's about $150 annually, but it's well worth it. The grounds are clean and they allow outside food and drink, so it can be cost effective. They have 2 splash pads and a treehouse playground for the kids. It can get HOT here, but the splash pads make it bearable.
Overall, the Phoenix Zoo is a better zoo than the other options hands down. If you care about the welfare of the animals, it's the only zoo you should visit.