为什么此代码忽略作者id

它不是忽略作者ID。但是使用该代码，您需要调用setup_postdata(), 像这样：

//global $post; // Uncomment if necessary.

$current_user = wp_get_current_user();
//$current_user->ID;

$post_ref = get_posts( array( \'author\' => $current_user->ID, \'numberposts\' => 1, \'cat\' => 31 ) );
foreach( $post_ref as $post ):
  setup_postdata( $post ):
  the_title(); echo get_the_ID();
endforeach;
wp_reset_postdata();