$n = mysqli_num_rows($result); // 获取数据条目数 ->15
$d = mysqli_num_fields($result); // 获取字段个数 -> 4
↓↓↓↓真相是↓↓↓↓↓(注意：颜色对应着看)
print_r($result);
// -> mysqli_result Object
( [current_field] => 0 [field_count] => 4 [lengths] => [num_rows] => 15 [type] => 0 )
原文：https://www.cnblogs.com/vaso-me/p/11223554.html