$b = $a?? $c ;相当于$b= isset($a)?$a:$c; $b = $a?: $c ;则是 $b = !empty($a) ? $a:$c; 相关文章: 2022-12-23 2022-12-23 2021-06-21 2021-12-31 2022-12-23 2021-08-22 2021-12-24 2021-11-06