It seems to do so but only some dependencies, since it auto install apache22 and php5 when I install Nagios 3.5. However, mysql server is not installed.

Is there any other configuration required for pkgng to auto install all the dependencies? Or under what circumstances are the dependencies not auto installed?

Thanks.

I have never used it and know little about it, still on 8.x, as with anything in FreeBSD there is the manual
freebsd.org

MySQL is not REQUIRED for Nagios (or other mentioned packages), the reason You CAN setup Nagios with MySQL does not mean that You HAVE to.

PKGng resolves and installs dependencies very fine.

Its also about HOW the above packages were compiled using Ports, if MySQL was not selected as an option for any of them, then it will not be a dependency.

IMHO if You are creating server its best to use FreeBSD Ports to install/compile all the modules You need (php/apache/mysql/...) then try to do that with packages which will have to be recompiled anyway if some module is missing.

In this case PKGng is good for 'build' dependencies, after You compile Your stack (php/mysql/apache/...), then LOCK them (pkg lock lang/php5 for example) in PKGng, so PKGng will not update them binary way.