infocse

Thank you very much @lorro, it works!

The only problem now is that array_shift excludes the name of the other categories
from the function.
ex.

product 1 (category:red)

product 2 (categories:green,red,yellow)

$single_cat = array_shift( $product_cats );
switch ($single_cat->name) {
  case 'red': // nb no break;
  case 'blue':
    echo '<span class="categoria">'.$single_cat->name.'</span>';
    break;
  default:
    // no action for anything other than red or blue
}

I can see the name of the category just in the first product,
so I presume that I have to change array_shift in something else, or am I wrong?

I found the function for categories selection in campaigns.php
at line 2268:

'<input data-placeholder="' . __( 'Select...', WYSIJA ) . '" name="category_ids" style="width: 300px" class="category_ids mailpoet-field-select2-terms" data-multiple="true" data-value=\'' . WJ_Utils::esc_json_attr( $_attr_init_selection ) . '\' value="' . esc_attr( implode( ',', $terms_selected ) ) . '" type="hidden">' .

I’ve try to change esc_attr( implode( ',', $terms_selected ) in esc_attr( implode( '+', $terms_selected ) but nothing is happen 🙁