Toggle php-mode and html mode dynamically

toggle-php-mode.el

;;; toggle-php-mode.el
;;; Toggle php-mode and html-mode.
;;; Version: 0.02: 2010/11/24
;;; Version: 0.01: 2010/05/08

(defvar php-html-major-mode 'html-mode
  "Major mode for editing html files with `php-mode'.")

(defvar php-activate-html-mode-command 'html-mode
  "Command that activates a major-mode for html."
  )

(defun preserve-region (beg end)
  (cond ((< (point) beg)
         (push-mark (point) nil t)
         (push-mark end nil t))
        ((> (point) end)
          (push-mark beg nil t)
          (push-mark (point) nil t))
        (t
         (push-mark beg nil t)
         (push-mark end nil t)
         )))

(defun php-change-major-mode-to-html ()
  (when (equal major-mode 'php-mode)
    (if (region-active-p)
        (progn
          (funcall php-activate-html-mode-command)
          (preserve-region (region-beginning) (region-end))
      (funcall php-activate-html-mode-command)))))

(defun php-change-major-mode-to-php ()
  (unless (equal major-mode 'php-mode)
    (if (region-active-p)
        (progn
          (php-mode)
          (preserve-region (region-beginning) (region-end)))
      (php-mode))))

(defun toggle-php-mode ()
  "Toggle php-mode and `php-html-major-mode' if necessary."
  (when (or (equal major-mode 'php-mode) (equal major-mode php-html-major-mode))
    (let ((php-beginning-position (save-excursion (search-backward "<?php" nil t)))
          (php-end-position (save-excursion (search-backward "?>" nil t))))
      
      (if (save-excursion
            (beginning-of-line)
            (looking-at "[ \t\s]+<[?]php"))
          (php-change-major-mode-to-php)
        (cond ((not (integerp php-beginning-position))
               (php-change-major-mode-to-html))
              ((and (integerp php-beginning-position) (not (integerp php-end-position)))
               (php-change-major-mode-to-php))
              ((and (integerp php-beginning-position) (integerp php-end-position))
               (if (> php-beginning-position php-end-position)
                   (php-change-major-mode-to-php)
                 (php-change-major-mode-to-html))))))))

(add-hook 'post-command-hook 'toggle-php-mode)