Coming to Craft after years with EE, I feel like a newbie again.
I painfully managed to built and install a basic plugin for craft3 with composer, (with a little help from the docs and NYstudio107's tutorial).
For now, the plugin does nothing, and to keep going, I would need to understand how to translate a pattern commonly used in EE. Get some data from a template, process it and return it.
Get tag data and parameters
$data_to_process = ee()->TMPL->tagdata; $process_param = ee()->TMPL->fetch_param('parameter');
Output content to template
ee()->return_data = $processed_data;
Ho do you do such things in craft ?