If you're having trouble, there are lots of resources you can turn to.
The official MongoDB IRC room is irc.freenode.net/#mongodb. This is the fastest way to get help.
» MongoDB's mailing list is a good (and usually very fast) way to get answers to questions.
Found a bug? Want a feature? Have a question? File it in the » PHP driver's bug tracker.
You can make the driver log all kinds of error messages as
E_NOTICE level PHP error messages. Have a look at the MongoLog for an example.
You can turn on (very) verbose debugging output by compiling the driver with the debugging flag.
$ ./configure CFLAGS=-DDEBUG
DEBUG turns on all debugging. You can also turn on specific debug flags. In the latest code, these flags are: