Show tabs in PHP code

emacs/.emacs.d/init.org

@@ -1100,6 +1100,20 @@
        (add-hook 'php-mode-hook #'electric-indent-local-mode)
      #+END_SRC
 
+*** Show tabs and spaces in indent
+
+    I'm working with some WordPress plugins nowadays and their style
+    guide insists on using tabs, not spaces... I'd like to know that
+    I'm following this rule.
+
+    #+BEGIN_SRC emacs-lisp
+      (defun oni:enable-whitespace-for-php ()
+        (setq whitespace-style '(face tabs tab-mark))
+        (whitespace-mode))
+
+      (add-hook 'php-mode-hook #'oni:enable-whitespace-for-php)
+    #+END_SRC
+
 * Load custom file
 
   I don't really use the Emacs customization interface much, but I