I program service scripts in PHP designed to be portable to other systems running PHP.  And while the same code works on my own site, a few people have reported some really gnarly errors when trying to run the code on their own sites.  Since I can't access their sites to see what the problem is, and I can only try and figure it out from the error messages they send me...
 
A list of error messages PHP returns, along with general descriptions as to what might have caused them would be invaluable for me.  I could also direct people there if their queries were simple enough.
 
Brian