Don’t hack your parent theme, use hooks!

If you are developing a WordPress child theme and need to add feature support to a registered custom post type, try using add_post_type_support(). By combining this function with the ‘init’ action hook you can make this modification without hacking the parent.

In the example below, I add thumbnail support to my parent theme’s existing ‘portfolio’ custom post type.

add_action('init','add_support');
function add_support(){
	add_post_type_support('portfolio','thumbnail');
}

Adding hooks to a child theme’s functions.php is the best practice when modifying a post type registered in a parent theme. It makes makes your work more manageable and most importantly prevents it from being overwritten.