The documentation on snippets in modx: http://rtfm.modx.com/display/revolution20/Snippets
Near the top of the doc it says: Note how we returned the code rather than echo'ed the content out. Never use echo in a Snippet - always return the output.
This doesn't display anything:
return $product_attribute $product_info[0][$column_name];
This does display:
echo $product_attribute $product_info[0][$column_name];
If I can't echo the content how do I get it to print in the html page?