Lately I've found some buffers get marked as modified right after activating php-mode. It happens only in emacs 25. I've bisected it down to commit 86eab80 which makes php-mode call php-syntax-propertize-function.

It turns out that normally, the calling code takes care of retaining the modification state. So the proper thing to do is take care of the modification state ourselves. The macro with-silent-modifications does exactly that. I'll create a patch for that in a minute.

Steps to reproduce:

• create a file, write a comment containing an apostrophe
• open the file in a buffer, activate php-mode

Expected result:

• (null (buffer-modified-p))

Actual result:

• (buffer-modified-p)