What is this syntax for in php-mode.el

["Lennart Borgman (gmail)" <lennart.borgman@gmail.com>]

I am looking at php-mode.el from Turadg. I can not understand this:

(defconst php-font-lock-syntactic-keywords
   (if xemacsp nil
     ;; Mark shell-style comments.  font-lock handles this in a
     ;; separate pass from normal syntactic scanning (somehow), so we
     ;; get a chance to mark these in addition to C and C++ style
     ;; comments.  This only works in GNU Emacs, not XEmacs 21 which
     ;; seems to ignore this same code if we try to use it.
     (list
      ;; Mark _all_ # chars as being comment-start.  That will be
      ;; ignored when inside a quoted string.
      '("\\(\#\\)"
        (1 (11 . nil)))
      ;; Mark all newlines ending a line with # as being comment-end.
      ;; This causes a problem, premature end-of-comment, when '#'
      ;; appears inside a multiline C-style comment.  Oh well.
      '("#.*\\([\n]\\)"
        (1 (12 . nil)))
      )))

What is it for? Does php use # as a comment somewhere?

And what about the format for the list entries? I tried to look at 
font-lock-syntactic-keywords, but I can not see that these entries 
follows the spec there.

How does this work?