In the latest article in his "Solar Shorts" series Richard Thomas looks at the Solar_Config component of the Solar framework and how callbacks can be used to extend its base functionality.

Solar_Config is a great configuration system but at times you find yourself wanting more, by itself Solar_Config has a few weaknesses. [...] You have a couple options, each have highs and lows related to how they work.

His example is of a custom callback (as defined in the main Solar_Config file for your site) that defines a "_postConfig" hook that lets you inject configuration information when the classes are loading instead of all up front.