Urlencode problem when querying taxonomy groups

I made a dynamic “list” of checkboxes based on custom taxonomies (from POST type.

foreach ($terms as $term) {
    $term_name = $term->name;
    echo "<p><input type=\"checkbox\" name=\"{$tax_name_cb}[]\" value=\"$term_name\" id=\"$term_name\" /><label for=\"$term_name\"> $cv2</label></p>";
}

The problem is that whenever I do a search, i get the following warning: Warning: urlencode() expects parameter 1 to be string, array given . The funny thing is, I DON’T get this warning when querying a custom post type the same way!

Anyway, if I for example change $tax_name_cb}[]\ to $tax_name_cb}\ I don’t get the warning, but then obviously I can’t search thru multiple checkbox groups.