can you set a default value to a custom field

Question

I'm looking to set a default value to a specific custom field, in case the client doesn't add into the custom field it already has a specific number associated with it.

one step deeper, I'd like it so if cat =22 is selected this custom field is automatically added into the post with a default that hopefully the client will add the proper number

I think this can be accomplished by a global function but my brain is just not processing this right now

Answer 1

You would not do this via a global, you simply use the default functionality of add_post_meta.

// your loop
if ( in_category(22)) {

    //check if the meta field has a value
    $meta_values = get_post_meta($post->ID, 'your_meta_key', true);

    if(empty($meta_values)){
    //add a default value
    add_post_meta($post->ID, 'your_meta_key', 'some default value');
    }
}

Reference: http://codex.wordpress.org/Custom_Fields

Answer 2

You can check it by adding a hook to save_post action. In this way all your posts will have default value for a custom field.

add_action( 'save_post', 'wpse8170_save_post', 10, 2 );
function wpse8170_save_post( $post_id, WP_Post $post ) {
    if ( ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) || !current_user_can( 'edit_post' ) ) {
        return;
    }

    if ( has_category( 22, $post_id ) && !get_post_meta( $post_id, 'my-custom-field', true ) ) {
        update_post_meta( $post_id, 'my-custom-field', 'my default value' );
    }
}