WordPress - Automatically disallow indexing on staging sites

gistfile1.txt

function theme_disallow_indexing_for_staging() {
	if (
		str_ireplace(array('staging-subdomain-1.com', 'dev-subdomain-2.net'), '', $_SERVER['SERVER_NAME']) != $_SERVER['SERVER_NAME']
		&& get_option('blog_public') == '1'
	) {
		add_action('pre_option_blog_public', '__return_zero');
	}
}
add_action('init', 'theme_disallow_indexing_for_staging');