[Solved] Where does printf() output go?

[JoshW]

This seems like a stupid question, but I can't figure it out.  When printf() is called in the PHP code, where is the output?

Update:

I found some indication that printf() output is sent to /dev/null, so I'm using log_error() instead.  Output goes to /var/log/system.log.

[ShadowFlare]

It depends on where the code is being used.  If it is a web gui or console program, the output should go there.