Recently I was working on a project where I was writing some PHP and HTML source code documentation and publishing it via WordPress. As you may know, the WordPress visual editor isn’t ideal when it comes to handling such code. Consequently, I went looking for a way to set the default editor to HTML rather than Visual. However, I didn’t want to cause the HTML editor to be the default across the entire site, so I created a custom post type for my code documentation. Then I changed the default editor for only that post type with the following piece of code:

add_filter('wp_default_editor', 'set_default_editor');

function set_default_editor( $type ) {
    global $post_type;
    if('code-doc' == $post_type) 
        return 'html';
    return $type;
}

All you need to do to use this piece of code is change “code-doc” to reflect the name of your custom post type.