Add Metabox to all custom post types

Question

Ok, I've looked through the forum here, but haven't found quite what I'm looking for. I wanted to see if it was possible to add a Metabox to all custom post types without the need to setup an array? Or, maybe just the CPTs created using Custom Post Types UI plugin?

Here's the code I'm testing, but it only shows up on regular Posts.

    add_meta_box( 'my-meta-box-id2', 'Enter your PDF location for your post category below:', 'cd2_meta_box_cb', 'post', 'normal', 'high' );

Answer 1

The 4th parameter for add_meta_box() is the post_type. So if you're calling it with post, it'll only show on WordPress's native posts.

Try this:

add_meta_box(
    'my-meta-box-id2',
    'Enter your PDF location for your post category below:',
    'cd2_meta_box_cb',
    'your_custom_post_type_name',
    'normal',
    'high'
);

If you have multiple post types you'd like to attach this to, this should work:

$post_types = array( 'post_type_1', 'post_type_2', ); // and so forth
foreach( $post_types as $post_type) {
    add_meta_box(
        'my-meta-box-id2',
        'Enter your PDF location for your post category below:',
        'cd2_meta_box_cb',
        $post_type,
        'normal',
        'high'
    );
}

(Whoops -- fixed the code to actually use the $post_type variable.)

Reference

Codex page for add_meta_box()

Answer 2

You can use this.If we want to add meta box to more than one posttypes then we have to use it inside array.We don't need foreach loop for get this.Just use post type array inside meta box.

add_meta_box(
    'my-meta-box-id2',
    'Enter your PDF location for your post category below:',
    'cd2_meta_box_cb',
    array('custom-posttype-1','custom-posttype-2','custom-posttype-3'),
    'normal',
    'high'
);

Answer 3

According to the docs: https://developer.wordpress.org/reference/functions/add_meta_box/ The 4th argument of add_meta_box function can accept arrays too.

$screen

(string|array|WP_Screen) (Optional) The screen or screens on which to show the box (such as a post type, 'link', or 'comment'). Accepts a single screen ID, WP_Screen object, or array of screen IDs. Default is the current screen.

Default value: null

So you can either create an array with your preferred post types:

$post_types = array( 'cpt1', 'cpt2', ... );
add_meta_box( 'my-meta-box', 'My Meta Box','display_my_meta_box', $post_types);

Or simply use the function get_post_types() to get the name of all post types:

$post_types = get_post_types();
add_meta_box( 'my-meta-box', 'My Meta Box','display_my_meta_box', $post_types);

https://codex.wordpress.org/Function_Reference/get_post_types

As it's said in the docs, you can set get_post_types( array( '_builtin' => false ) ); to ignore the wp default post types.