Write a simple text manipulation script for a website

I need someone to write a script and a very simple frontend that will manipulate text pasted into a box.

The text pasted in will be in the format:

[URL]

[Header 1]
[Translation of header 1]

[Paragraph 1]
[Translation of paragraph 1]

...

[URL]

[Username]
[Comment 1]
[Translation of comment 1]

...
And I want the output to be:

[URL]

[code snippet 1][Header 1][code snippet 2][Translation of header 1][code snippet 3]

[code snippet 4][Paragraph 1][code snippet 5][Translation of paragraph 1][code snippet 6]

...

[URL]

[Username]
[code snippet 7][Comment 1][code snippet 8][Translation of comment 1][code snippet 9]

...

I would like the script to work with any number of paragraphs and comments. Double quote characters should be escaped out in the text, but not in the code snippets.

The frontend does not need to be complex, just a page with two boxes on it, one to paste the input into, a button, and another to copy the output from.

The code snippets should also be easily visible in the script's code to allow for future modifications.

I believe that PHP will be the easiest tool for this, but provided it runs on a LAMP server, you can use whatever you feel best.

I've attached before and after samples of what I want so you can see for yourself what I mean.