I am smashing my head against some code. Here is the situation: I have one post in 3 different categories, this post has to be visible in "category 1" with the single1.php, in "category 2" with single2.php and in "category 3" with single3.php.

Obviously the 3 single.php pages have a different template inside. For example the single1.php shows pictures and the_content(); single2.php shows pictures and comments; single3.php shows the reviews.

I know that in single.php I can use the if/else but I cannot figure out if the same post is in 3 different categories.

Any help please?