I've been working on your code for about three hours. I removed the "admin" functionality (and therefore the upload), because it wasn't something that I wanted/needed, and it didn't work off the bat for me. Pictures now display 4:3 or 3:4, but I'm going to fix it to work for any aspect ratio in the morning. I squashed all of the undefined bugs that I ran into.
When you append to a variable in a loop using .=, you need to declare the variable first.
Code:
$my_string = "";
while($some_flag){
$my_string .= "bob ";
}
This prevents those nasty undefined variable errors that were all over the place.