The "t" modifier is probably a result of your "additional image" filename having "/t" in it somewhere, such as "widgets/trip1.jpg".

So, to work around that, change your preg_match logic to use something other than / as the modifier symbol.

One of the posts above quotes the following code:
Code:
if(preg_match('/\Q' . $products_image_base . '\E/i', $file) == 1) {
If you change that to the following, it may accommodate your added slashes in your additional-image filename:
Code:
if(preg_match('~\Q' . $products_image_base . '\E~i', $file) == 1) {