Code snippet to display ID gives critical error

Based on this post, I added the code snippet below to my WordPress site, as to display the ID in the Posts section of each post. However, it returns "critical error". Any idea what is wrong with this code?

add_filter( 'manage_posts_columns', 'column_register_wpse_101322' ); add_filter( 'manage_posts_custom_column', 'column_display_wpse_101322', 10, 3 );  function column_register_wpse_101322( $  columns ) {     $  columns['uid'] = 'ID';     return $  columns; }  function column_display_wpse_101322( $  empty, $  column_name, $  post_id ) {     if ('uid' != $  column_name) {return $  empty;}     return "$  post_id"; }