This bug was also present in earlier version, as the
http://www.freepbx.org/trac/ticket/2792 was.
Anyway this is worst.
If you try to get the second graph in the reports-->DaylyLoad?, you succed in it
only if the calls are not too much.
I can't explain better, but looking on a server medium-loaded (abount 6 hundred calls per hour) you get the graph only on the hours containing less calls.
If I try to get the graph beetween 9 and 10, I get a red cross image. If I filter the calls in that hour using only the zap channels calls, I get the graph, idicating a maximum load of about 10 calls.
So it is not a missing php problem, but perhaps a bad dimensioned variable (maybe?)
No errors are detected into apache log, nor in the messages log.
I am using opensuse 10.2, kernel 2.6.18.8-0.5-default #1 SMP , php5.
Where can I check and what can I do to help you to solve this issue ?