You cannot override those functions.
What is it you're trying to accomplish? That would help us give you a better direction to go.
Ok, I want to change tags delimiter from ',' to '-' by changing implode and explode functions. how can I do that properly so that all tags inputs and outputs are affected?
Changing the tag delimiter would be difficult to do correctly. Here's one hack:
$tags = explode("-", get_input("tags", "")); set_input("tags", implode(",", $tags));
This should work for each form that uses "tags" as the name of the input/tags view, but blindly rewriting input is a brittle solution.
My advice is to not do this.
info@elgg.org
Security issues should be reported to security@elgg.org!
©2014 the Elgg Foundation
Elgg is a registered trademark of Thematic Networks.
Cover image by Raül Utrera is used under Creative Commons license.
Icons by Flaticon and FontAwesome.