Disable warning from irony for PHP files

[Sanjeev Sariya]

Hi Emacs Community,

Version: GNU Emacs 24.5.1

Please bear with me, I'm a learner on how to enable and play around config file 
in emacs for different languages. 

I've installed package for php : php-mode
For which the config file looks:

(require 'php-mode)
(add-to-list 'auto-mode-alist '("\\.php$" . php-mode))
(add-to-list 'auto-mode-alist '("\\.inc$" . php-mode))


I've irony, and company-irony mode added in my init.el, for which init.el looks 
like:

(eval-after-load 'company
    '(add-to-list 'company-backends 'company-irony))

(require 'irony)
(add-hook 'after-init-hook #'global-company-mode)
(add-hook 'c++-mode-hook 'irony-mode)
(add-hook 'c-mode-hook 'irony-mode)

When I open alpha.php, I get following warning:

Warning (irony): Major mode is unknown to Irony, see 
`irony-supported-major-modes'.

I know irony doesn't support php file. How can I disable irony to work while 
working with .php or any other language, or say restrict it to c, cpp, .h, .hpp 
files?

Any guidance shall be highly appreciated