emacs autoload modes

Question 1

As liu says, you use add-hook to specify that an action be run when a particular mode is started. Documentation here. Hooks are analogous to events in C#, or the observer pattern in OOP.

Every mode should define a hook that is run when that mode is started, eg. for a mode named java-mode there is a corresponding hook called java-mode-hook. add-hook lets you wire an action to this hook:

(add-hook 'java-mode-hook 'my-action)

You can use anonymous lambda functions to define the action in-place, like so:

(add-hook 'java-mode-hook (lambda () (message "hello from java-mode")))

This will print a message whenever you start up java mode.

It is usually better to define a named function for the purpose. If you use named functions, add-hook will ensure the same function is not called multiple times.

  (defun hello () 
    (message "hello from java-mode"))

  (add-hook 'java-mode-hook 'hello)

Language editing modes are derived from prog-mode. If you want to run an action when you start up any programming language mode, you add your function to prog-mode-hook.

You need to manually configure autocomplete mode for each mode you want to use it in. For each mode, add that mode to the ac-modes list:

(add-to-list 'ac-modes 'java-mode)

As a side note, you will want to use flyspell-prog-mode for programming language modes, so you only receive spelling suggestions in comments and string literals.

(defun on-prog-mode ()
  (flyspell-prog-mode t))

(add-hook 'prog-mode-hook 'on-prog-mode)

And you will probably want to use flycheck instead of the older flymake. Flycheck is under active development and has checkers for php.

Question 2

you can add just like below:

(global-auto-complete-mode t)
(yas-global-mode 1)

then update below accordingly:

(add-hook 'php-mode-hook (lambda () (flyspell-mode 1)))
(add-hook 'php-mode-hook (lambda()(gtags-mode 1)))