What is this syntax for in php-mode.el

[Lennart Borgman (gmail)]

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?