I haven't tried hooking a ph probe up but I have used several of the DS18B20 probes. I have used the waterproof ones in my fishtank and waterproof outdoor camera cases.
They are really simple to hook up, all you need is a 4.7k resistor. Since they use the one wire protocol, multiple sensors can be hooked up to the same GPIO pin. There are alot of tutorials available by searching Google. Adafruit does have an excellent tutorial that helped me figure out how to wire them.
https://learn.adafruit.com/adafruits-ra ... g/hardware
Starting on Thanksgiving of last year, I have had between 3 to 10 of them running continuously and recording the temperature data in a MySQL database. I currently have 311,474 temperature readings. Unlike the DHT11 probes, I haven't had any wild or questionable readings with the DS18B20. I'm more than happy with this sensor.
If you happen to hookup a ph probe, make sure to come back and comment on your experience. I would be interested in knowing how it works for you. I'm red-green colorblind, and my girlfriend hates reading the ph level for me. Adding a ph probe is on my to-do list.