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//edit custom field placeholder text in title box
function wpb_change_title_text( $title ){
     $screen = get_current_screen();
 
     if  ( 'people' == $screen->post_type ) {
          $title = 'Enter full name, first and last';
     }
 
     return $title;
}
 
add_filter( 'enter_title_here', 'wpb_change_title_text' );