您可以使用the_content 过滤以在输出内容之前修改内容。

function my_the_content_filter( $content ) {
    // maybe limit to archive or single cpt display?
    if( is_post_type_archive( \'your-cpt\' )
        || is_singular( \'your-cpt\' ) ){
        global $post;
        $meta = get_post_meta( $post->ID, \'some-key\', true );
        if( false === $meta ){
            return $content . \'some extra content\';
        }
    }
    return $content;
}
add_filter( \'the_content\', \'my_the_content_filter\' );