Converting snake_case to PascalCase

Is there an effective way, maybe with regex, to change the following text pattern?

I have a string like abc_def_ghi_jkl. I want to replace it to AbcDefGhiJkl. I currently use the following code to change it. Is there a more effective way than this?

implode('',array_map('ucfirst',explode('_',$string)));

More effective solution:

str_replace('_', '', ucwords($key, '_'));

From Gears library

StackExchange Code Review Q#48593, answer score: 26