It's Subword mode.

Author: zonuexe

php-mode.el

@@ -422,7 +422,7 @@ local variables, set NIL."
     ;;
     ;;     https://www.gnu.org/software/emacs/manual/html_node/ccmode/Subword-Movement.html
     ;;
-    ;; for more information about Submode Word.
+    ;; for more information about Subword mode.
     (define-key map (kbd "C-c C-w") 'subword-mode)
 
     ;; We inherit c-beginning-of-defun and c-end-of-defun from CC Mode