After the update at the beginning of last week, I had a Master/Detail that started generating seemingly random PHP errors. I was finally able to track it down to the PDF button. If I remove the button, the error goes away, but it seems to only affect Master/Detail form/grid. My Master/Detail has a form app for the Master and a grid app for the Detail. I was able to recreate it in a blank project which I exported in the links below:
https://www.dropbox.com/s/5b915d587rnrlwp/baworders.sql?dl=0
https://www.dropbox.com/s/4f7han9zbgepofq/SC8-PDF%20bug.zip?dl=0
I was also able to track it down in the PHP code itself, linked below. However, this was generated from my actual project, not the blank project above, but it might still be of some help.
https://www.dropbox.com/s/4ra6qlwrcxfmxro/badform.txt?dl=0
-Chris