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Modify a Custom Post Type after it's been registered

June 09, 2016

Today I was tasked with adding functionality to an existing custom post type. The problem was, the CPT was being registered in a plugin which I could not edit.

After some digging, I found there’s a filter for that (found in post.php) which allows you to modify a custom post type, after it’s been registered some other way.

apply_filters( ‘register_post_type_args’, $args, $post_type );

Hooking into that filter, allowed me to pass additional options to an existing CPT:

* Filter the Products CPT to register more options.
* @param $args array The original CPT args.
* @param $post_type string The CPT slug.
* @return array
function grd_client_filter_products_cpt( $args, $post_type ) {
// If not Products CPT, bail.
if ( 'products' !== $post_type ) {
return $args;
// Add additional Products CPT options.
$products_args = array(
'has_archive' => true,
'supports' => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'custom-fields', 'page-attributes' ),
// Merge args together.
return array_merge( $args, $product_args );
add_filter( 'register_post_type_args', 'grd_client_filter_products_cpt', 10, 2 );

Now “Products” has an archive, along with some other meta boxes in the post editor. Nice!

Director of Engineering @WebDevStudios / Author & Editor @WileyGlobal. Read more about me.